Document:

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                                                                    Exhibit 4.5

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                            W. R. BERKLEY CORPORATION

                                       to

                              THE BANK OF NEW YORK
                                   as Trustee

                                -----------------

                          SUPPLEMENTAL INDENTURE NO. 1

                            Dated as of July 26, 2005

                                -----------------

                     6.750% Subordinated Debentures Due 2045

                               -------------------

================================================================================

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                                                                     Exhibit 4.6

                                TABLE OF CONTENTS

                                    ARTICLE I
                       RELATION TO INDENTURE; DEFINITIONS

                                   ARTICLE II
                            THE SERIES OF SECURITIES

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Section 2.1     Title of the Securities..........................................................    2

Section 2.2     Limitation on Aggregate Principal Amount; Date of Securities.....................    2

Section 2.3     Principal Payment Dates..........................................................    2

Section 2.4     Interest and Interest Rates......................................................    2

Section 2.5     Extension of Interest Payment Period.............................................    3

Section 2.6     Place of Payment.................................................................    4

Section 2.7     Redemption.......................................................................    4

Section 2.8     Preferred Security Holders' Rights...............................................    5

Section 2.9     Additional Covenants.............................................................    6

Section 2.10    Denomination.....................................................................    6

Section 2.11    Currency.........................................................................    6

Section 2.12    Registered Securities; Form......................................................    6

Section 2.13    Global Securities Upon Liquidation of Trust......................................    7

Section 2.14    Defeasance and Covenant Defeasance...............................................    8

Section 2.15    Registrar and Paying Agent.......................................................    8

Section 2.16    Additional Provisions Regarding Amendments.......................................    8

Section 2.17    Additional Provisions Regarding Assignment.......................................    8

Section 2.18    Miscellaneous Expenses...........................................................    9

                                             ARTICLE III
                                       MISCELLANEOUS PROVISIONS

Section 3.1     Adoption of the Supplemental Indenture...........................................    9

Section 3.2     Counterparts.....................................................................    9

Section 3.3     Governing Law....................................................................    9
</TABLE>

                                       i
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                            W. R. BERKLEY CORPORATION

                          SUPPLEMENTAL INDENTURE NO. 1

                                  $250,000,000

                     6.750% Subordinated Debentures Due 2045

      SUPPLEMENTAL INDENTURE NO. 1 (this "Supplemental Indenture No. 1"), dated
as of July 26, 2005 from W. R. BERKLEY CORPORATION, a Delaware corporation (the
"Company"), to THE BANK OF NEW YORK, a New York banking corporation, as trustee
(the "Trustee").

                                    Recitals

      The Company has heretofore executed and delivered to the Trustee a
Subordinated Indenture, dated as of the date hereof, as supplemented and amended
by this Supplemental Indenture No. 1 (as so supplemented and amended, the
"Indenture"), providing for the issuance from time to time of series of the
Company's Securities. Capitalized terms used but not defined herein shall have
the meanings ascribed to such terms in the Indenture.

      Section 3.1 of the Indenture provides for various matters with respect to
any series of Securities issued under the Indenture to be established in an
indenture supplemental to the Indenture.

      Section 9.1 of the Indenture provides for the Company and the Trustee to
enter into an indenture supplemental to the Indenture to establish the form or
terms of Securities of any series as provided by Sections 2.1 and 3.1 of the
Indenture.

      For and in consideration of the premises and the issuance of the series of
Securities provided for herein, it is mutually covenanted and agreed as follows
for the equal and ratable benefit of the Holders of the Securities of such
series:

                                   ARTICLE I

                       RELATION TO INDENTURE; DEFINITIONS

      Section 1.1. This Supplemental Indenture No. 1 constitutes an integral
part of the Indenture.

      Section 1.2. For all purposes of this Supplemental Indenture No. 1:

      (a) Capitalized terms used herein without definition shall have the
meanings specified in the Indenture;

      (b) All references herein to Articles and Sections, unless otherwise
specified, refer to the corresponding Articles and Sections of this Supplemental
Indenture No. 1; and

                                       1
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      (c) The terms "herein", "hereof", "hereunder" and other words of similar
import refer to this Supplemental Indenture No. 1.

                                   ARTICLE II

                            THE SERIES OF SECURITIES

            Section 2.1 Title of the Securities.

      There shall be a series of Securities designated the "6.750% Subordinated
Debentures Due 2045" (hereinafter, the "Securities").

            Section 2.2 Limitation on Aggregate Principal Amount; Date of
Securities.

      The aggregate principal amount of the Securities shall be limited to
$250,000,000. Each Security shall be dated the date of its authentication.

            Section 2.3 Principal Payment Dates.

      The principal amount of the Securities Outstanding (together with any
accrued and unpaid interest thereon) shall be payable in a single installment on
July 26, 2045.

            Section 2.4 Interest and Interest Rates.

      The rate of interest on each Security shall be 6.750% per annum, accruing
from July 26, 2005 and, subject to Section 2.5 hereof, interest shall be
payable, in arrears, on January 30, April 30, July 30 and October 30 of each
year (each an "Interest Payment Date"), commencing October 30, 2005. The amount
of interest payable on any Interest Payment Date shall be computed on the basis
of twelve 30-day months and a 360-day year and, for any period that is shorter
than a full 90-day quarter, will be calculated on the basis of the actual number
of days elapsed in such period. In the event that any date on which interest is
payable on a Security is not a Business Day, then payment of the interest
payable on such date will be made on the next succeeding day which is a Business
Day (and without any interest or other payment in respect of any such delay),
except that, if such Business Day is in the next succeeding calendar year, such
payment shall be made on the immediately preceding Business Day, in each case
with the same force and effect as if made on such date. The interest so payable
on any Security which is punctually paid or duly provided for on any Interest
Payment Date shall be paid to the Person in whose name such Security is
registered at the close of business on the Regular Record Date for such Interest
Payment Date, which, for purposes of this Supplemental Indenture No. 1, shall be
the Business Day preceding such Interest Payment Date; provided, that in the
event the Securities shall not continue to remain in book-entry only form, the
record dates shall be the January 15, April 15, July 15 and October 15 prior to
the applicable Interest Payment Date. The interest so payable on any Security
which is not punctually paid or duly provided for on any Interest Payment Date
shall forthwith cease to be payable to the Person in whose name such Security is
registered on the relevant Regular Record Date, and such defaulted interest
shall instead be payable to the Person in whose name such Security is registered
on the special record date or other specified date determined in accordance with
the Indenture.

                                       2
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            Section 2.5 Extension of Interest Payment Period.

      Notwithstanding anything contained herein or in the Indenture to the
contrary, the Company shall have the right at any time, and from time to time,
during the term of the Securities to defer payments of interest by extending the
interest payment period to the next Interest Payment Date by one or more
quarterly periods not exceeding 20 consecutive quarters (each such period, an
"Extension Period"), but no such Extension Period may extend beyond July 26,
2045. At the end of any such Extension Period, the Company shall pay all
interest then accrued and unpaid (including any Additional Sum, as hereinafter
defined) together with interest thereon compounded quarterly at the rate
specified for the Securities to the extent permitted by applicable law
("Compound Interest"); provided, that during any such Extension Period, (a) the
Company shall not declare or pay dividends on, make any distribution with
respect to, or redeem, purchase, acquire or make a liquidation payment with
respect to any of its Capital Stock (other than (i) purchases or acquisitions of
shares of the Company's Common Stock in connection with the satisfaction by the
Company of its obligations under any employee benefit plans or the satisfaction
by the Company of its obligation pursuant to any contract or security requiring
it to purchase shares of its Common Stock, (ii) as a result of a
reclassification of the Company's Capital Stock or the exchange or conversion of
one class or series of the Company's Capital Stock for another class or series
of its Capital Stock, (iii) the purchase of fractional interests in shares of
the Company's Capital Stock pursuant to an acquisition or the conversion or
exchange provisions of such Capital Stock or the security being converted or
exchanged and (iv) redemptions or purchases pursuant to the Company's Rights
Agreement dated as of May 11, 1999, as amended, between the Company and Wells
Fargo Bank Minnesota, N.A. as successor in interest to ChaseMellon Shareholder
Services, LLC (the "Rights Agreement")), (b) the Company shall not make any
payment of principal, premium, if any, or interest on or repay, repurchase or
redeem any debt securities issued by the Company that rank pari passu with or
junior to the Securities and (c) the Company shall not make any guarantee
payments with respect to the foregoing (other than pursuant to the Preferred
Securities Guarantee Agreement, dated as of July 26, 2005, of the Company (the
"Preferred Guarantee") with respect to the 6.750% Trust Originated Preferred
Securities (the "Preferred Securities") issued by W. R. Berkley Capital Trust II
(the "Trust"), the Common Securities Guarantee Agreement, dated as of July 26,
2005, of the Company (the "Common Guarantee" and together with the Preferred
Guarantee, the "Guarantees") with respect to the 6.750% Trust Originated Common
Securities (the "Common Securities" and together with the Preferred Securities,
the "Trust Securities") issued by the Trust and the Common Securities Guarantee
Agreement, dated as of December 20, 1996 (the "Common Securities Guarantee
Agreement"), and the Capital Securities Guarantee Agreement, dated as of June 6,
1997 with respect to the 8.197% Capital Securities) (the "Capital Securities
Guarantee Agreement")). Prior to the termination of any such Extension Period,
the Company may further defer payments of interest by extending the interest
payment period; provided, however, that, such Extension Period, including all
such previous and further extensions, may not exceed 20 consecutive quarters or
extend beyond the Stated Maturity. Upon the termination of any Extension Period
and the payment of all amounts then due, the Company may commence a new
Extension Period, subject to the terms set forth in this section.

      No interest shall be due and payable during any Extension Period, except
at the end thereof, but the Company may prepay at any time all or any portion of
the interest accrued during an Extension Period. If the Property Trustee (as
defined in the Amended and Restated Trust

                                       3
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Agreement of W. R. Berkley Capital Trust II, dated as of July 26, 2005 (the
"Trust Agreement")) shall be the sole holder of the Securities, the Company
shall give the Administrative Trustees (as defined in the Trust Agreement), the
Property Trustee (as defined in the Trust Agreement) and the Trustee notice of
its selection of such Extension Period one Business Day prior to the earlier of
(i) the date distributions on the Preferred Securities are payable or (ii) the
date the Administrative Trustees are required to give notice of the record date
or the date such distribution is payable to the New York Stock Exchange (or
other applicable self-regulatory organization) or to holders of the Preferred
Securities, but in any event at least one Business Day before such record date.
If the Property Trustee shall not be the sole holder of the Securities, the
Company shall give the holders of the Securities notice of its selection of such
Extension Period at least 10 Business Days prior to the earlier of (i) the
Interest Payment Date or (ii) the date upon which the Company is required to
give notice of the record or payment date of such interest payment to the New
York Stock Exchange (or other applicable self-regulatory organization) or to
holders of the Securities. The quarter in which any notice is given pursuant to
this Section 2.5 shall be counted as one of the 20 quarters permitted in the
maximum Extension Period permitted hereunder.

            Section 2.6 Place of Payment.

      The Place of Payment where the Securities issued in certificated form may
be presented or surrendered for payment, where such Securities may be
surrendered for registration of transfer or exchange and where notices and
demands to and upon the Company in respect of such Securities and the Indenture
may be served shall be the Corporate Trust Office of the Trustee; provided,
however, that payment of interest may be made at the option of the Company by
checks mailed to the Holders at such addresses as shall appear in the Security
Register. Notwithstanding the foregoing, so long as the Holder of any Securities
is the Property Trustee, the payment of the principal of and interest (including
Compound Interest and Additional Sums, if any) on such Securities held by the
Property Trustee will be made at such place and to such account as may be
designated by the Property Trustee.

            Section 2.7 Redemption.

      Subject to the terms and conditions of Article 10 of the Indenture:

      (a) Optional Redemption. The Company may redeem the Securities in whole at
any time or in part from time to time, in each case on or after July 26, 2010,
but prior to the Stated Maturity, upon not less than 30 nor more than 60 days'
notice, at a redemption price equal to 100% of the principal amount of the
Securities to be redeemed plus any accrued and unpaid interest, including
Additional Sums, if any, to the date fixed for redemption (the "Redemption
Price").

      (b) The Company will have the right at any time to dissolve the Trust and
cause the Securities to be distributed to the holders of the Trust Securities in
accordance with the Trust Agreement.

      (c) Special Event Redemption.

                                       4
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      (i) If, at any time, a Tax Event or an Investment Company Event (each a
"Special Event") has occurred and is continuing, the Company shall have the
right, upon not less than 30 nor more than 60 days notice, to redeem the
Securities in whole but not in part, for cash in the amount of the Redemption
Price, within 90 days following the occurrence of such Special Event, and,
following such redemption, Trust Securities with an aggregate liquidation amount
equal to the aggregate principal amount of the Securities so redeemed shall be
redeemed by the Trust at the Redemption Price; provided, however, that if at the
time there is available to the Company or the Trust the opportunity to
eliminate, within such 90 day period, the Tax Event by taking some ministerial
action, such as filing a form or making an election or pursuing some other
similar reasonable measure that has no adverse effect on the Trust, the Company
or the holders of the Trust Securities, the Company or the Trust will pursue
such measure in lieu of a redemption. If the Company does not elect either to
distribute the Securities to the holders of the Preferred Securities in
liquidation of the Trust or to redeem the Securities, the Trust Securities shall
remain outstanding and, in the event a Special Event is continuing, Additional
Sums (as defined in Section 2.18 hereof) will be payable on the Securities.

      (d) The Securities are not entitled to the benefit of any sinking fund.

      (e) If Securities are distributed to the holders of the Preferred
Securities, (i) the Company will use its best efforts to cause the Securities to
be listed on the New York Stock Exchange or on such other exchange as the
Preferred Securities are then listed, and (ii) the Indenture, this Supplemental
Indenture No. 1 and the terms of the Securities may, thereafter, be modified or
amended with the consent of not less than 66-2/3% in principal amount of the
Securities at any time Outstanding; provided, however, that no such modification
or amendment may, without the consent of the Holder of each Security affected
thereby, (A) extend the stated maturity of the principal of any Security, or
reduce the principal amount thereof or reduce the rate or extend the time of
payment of interest thereon (other than as provided in Section 2.5 of this
Supplemental Indenture No. 1), or reduce any amount payable on redemption
thereof or change the Currency in which the principal thereof or interest
thereon is payable or impair the right to institute suit for the enforcement of
any payment on any Security when due, or (B) reduce the aforesaid principal
amount of Securities, the consent of the Holders of which is required for any
such modification.

            Section 2.8 Preferred Security Holders' Rights.

      If an Event of Default under Section 5.1(1) or 5.1(2) of the Indenture
with respect to the Securities has occurred and is continuing, then a holder of
Preferred Securities may directly institute a proceeding for enforcement of
payment to such holder directly of the principal of or interest on the
Securities having a principal amount equal to the aggregate liquidation amount
of the Preferred Securities of such holder on or after the respective due date
specified in the Securities. The holders of Preferred Securities will not be
able to exercise directly any other remedy available to the holders of the
Securities under this Supplemental Indenture No. 1 or under the Indenture unless
the Property Trustee fails to do so.

                                       5
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            Section 2.9 Additional Covenants.

      The Company agrees that if (i) there shall have occurred any event that
would constitute an Event of Default or (ii) the Company shall be in default
with respect to its payment of any obligations under the Preferred Guarantee or
Common Guarantee, or (iii) the Company shall have given notice of its election
to defer payments of interest on the Securities by extending the interest
payment period as provided in this Supplemental Indenture No. 1 and such period,
or any extension thereof, shall be continuing, then (a) the Company shall not
declare or pay any dividend on, make any distribution with respect to, or
redeem, purchase, acquire or make a liquidation payment with respect to any of
its Capital Stock (other than (i) purchases or acquisitions of shares of the
Company's Common Stock in connection with the satisfaction by the Company of its
obligations under any employee benefit plans or the satisfaction by the Company
of its obligation pursuant to any contract or security requiring it to purchase
shares of its Common Stock, (ii) as a result of a reclassification of the
Company's Capital Stock or the exchange or conversion of one class or series of
the Company's Capital Stock for another class or series of its Capital Stock,
(iii) the purchase of fractional interests in shares of the Company's Capital
Stock pursuant to an acquisition or the conversion or exchange provisions of
such Capital Stock or the security being converted or exchanged, and (iv)
redemptions or purchases pursuant to the Rights Agreement), (b) the Company
shall not make any payment of principal, premium, if any, or interest on or
repay, repurchase or redeem any debt securities issued by the Company that rank
pari passu with or junior to the Securities, and (c) the Company shall not make
any guarantee payments with respect to the foregoing (other than pursuant to
either of the Guarantees, the Common Securities Guarantee Agreement and the
Capital Securities Guarantee Agreement).

      The Company agrees (i) to directly or indirectly maintain 100% ownership
of the Common Securities; provided, however, that any permitted successor of the
Company under the Indenture may succeed to the Company's ownership of such
Common Securities, (ii) not to voluntarily terminate, wind-up or liquidate the
Trust, except (a) in connection with a distribution of Securities to the holders
of the Preferred Securities in liquidation of the Trust, or (b) in connection
with certain mergers, consolidations or amalgamations permitted by the Trust
Agreement and (iii) to use its reasonable efforts, consistent with the terms and
provisions of the Trust Agreement, to cause the Trust to remain a grantor trust
and not to be classified as an association taxable as a corporation for United
States federal income tax purposes.

            Section 2.10 Denomination.

      The Securities shall be issuable in denominations of $1,000 and integral
multiples thereof.

            Section 2.11 Currency.

      Principal and interest on the Securities shall be payable in Dollars.

            Section 2.12 Registered Securities; Form.

      Except as provided in Section 2.13, the Securities shall be issued as
Registered Securities, without coupons and shall be registered in the name of
The Bank of New York, as Property

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Trustee, and its permitted registered assigns. The Securities shall be
substantially in the form attached as Exhibit A hereto.

            Section 2.13 Global Securities Upon Liquidation of Trust.

      (a) If, in accordance with the Trust Agreement, the Trust is to be
dissolved and the Securities held by the Property Trustee are to be distributed
to the holders of the Trust Securities:

      (i) the Securities in certificated form shall be presented to the Trustee
by the Property Trustee in exchange for a global Security in an aggregate
principal amount equal to the aggregate principal amount of all outstanding
Securities (a "Global Security") to be registered in the name of the Depositary
(as defined in the Trust Agreement), or its nominee, and delivered by the
Trustee to the Depositary for crediting to the accounts of its participants
pursuant to the instructions of the Administrative Trustees (as defined in the
Trust Agreement). The Company upon any such presentation shall execute a Global
Security in such aggregate principal amount and deliver the same to the Trustee
for authentication and delivery in accordance with the Indenture and this
Supplemental Indenture No. 1. Payments on Securities issued as Global Securities
will be made to the Depositary; and

      (ii) if any Preferred Securities are held in non book-entry certificated
form, the Securities in certificated form may be presented to the Trustee by the
Property Trustee and any Preferred Security Certificate (as defined in the Trust
Agreement) which represents Preferred Securities other than Preferred Securities
held by the Clearing Agency (as defined in the Trust Agreement) or its nominee
("Non Book-Entry Preferred Securities") will be deemed to represent beneficial
interests in Securities presented to the Trustee by the Property Trustee having
an aggregate principal amount equal to the aggregate liquidation amount of the
Non Book-Entry Preferred Securities until such Preferred Security Certificates
are presented to the Registrar for transfer or reissuance at which time such
Preferred Security Certificates will be canceled and a Security, registered in
the name of the holder of the Preferred Security Certificate or the transferee
of the holder of such Preferred Security Certificate, as the case may be, with
an aggregate principal amount equal to the aggregate liquidation amount of the
Preferred Security Certificate canceled, will be executed by the Company and
delivered to the Trustee for authentication and delivery in accordance with the
Indenture and this Supplemental Indenture No. 1. On issue of such Securities,
Securities with an equivalent aggregate principal amount that were presented by
the Property Trustee to the Trustee will be deemed to have been canceled.

      (b) Unless and until it is exchanged for Securities in registered form, a
Global Security may be transferred, in whole but not in part, only to another
nominee of the Depositary, or to a successor Depositary selected or approved by
the Company or to a nominee of such successor Depositary.

      (c) If at any time the Depositary notifies the Company that it is
unwilling or unable to continue as Depositary or if at any time the Depositary
for such series shall no longer be registered or in good standing under the
Securities Exchange Act of 1934, as amended, or other applicable statute or
regulation, and a successor Depositary for such series is not appointed by the
Company within 90 days after the Company receives such notice or becomes aware
of such condition, as the case may be, the Company will execute, and, subject to
Article III of the

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Indenture, the Trustee, upon written notice from the Company, will authenticate
and deliver the Securities in definitive registered form without coupons, in
authorized denominations, and in an aggregate principal amount equal to the
principal amount of the Global Security in exchange for such Global Security. In
addition, the Company may at any time determine that the Securities shall no
longer be represented by a Global Security. In such event the Company will
execute, and subject to Section 3.3 of the Indenture, the Trustee, upon receipt
of an Officer's Certificate evidencing such determination by the Company, will
authenticate and deliver the Securities in definitive registered form without
coupons, in authorized denominations, and in an aggregate principal amount equal
to the principal amount of the Global Security in exchange for such Global
Security. Upon the exchange of the Global Security for such Securities in
definitive registered form without coupons, in authorized denominations, the
Global Security shall be canceled by the Trustee. Such Securities in definitive
registered form issued in exchange for the Global Security shall be registered
in such names and in such authorized denominations as the Depositary, pursuant
to instructions from its direct or indirect participants or otherwise, shall
instruct the Trustee in writing. The Trustee shall deliver such Securities to
the Depositary for delivery to the Persons in whose names such Securities are so
registered.

            Section 2.14 Defeasance and Covenant Defeasance.

      The provisions of Section 4.2 of the Indenture shall apply to the
Securities.

            Section 2.15 Registrar and Paying Agent.

      The Trustee shall initially serve as Registrar and Paying Agent.

            Section 2.16 Additional Provisions Regarding Amendments.

      So long as the Holder of the Securities is the Trust, the terms of the
Securities may be amended by mutual consent of the Company and the Trust in the
manner they shall agree; provided, however, that, so long as any of the
Preferred Securities remain outstanding, no such amendment shall be made that
adversely affects the holders of the Preferred Securities, no termination of the
Securities shall occur, and no Event of Default or compliance with any covenant
under the Securities may be waived by the Trust, without the prior approval of
the holders of at least 66-2/3% in liquidation preference of all Preferred
Securities then outstanding, in writing or at a duly constituted meeting of such
holders.

            Section 2.17 Additional Provisions Regarding Assignment.

      The Company shall have the right at all times to assign any of its rights
or obligations under the Securities to a direct or indirect wholly-owned
Subsidiary of the Company; provided, however, that, in the event of any such
assignment, the Company shall remain jointly and severally liable for all such
obligations. So long as the Trust is the Holder of the Securities, the Trust may
not assign any of its rights under the Securities, other than in connection with
a merger or consolidation or sale of assets or exchange permitted under the
terms of the Preferred Securities. Subject to the foregoing, the Securities
shall be binding upon and inure to the benefit of the Company and the Trust and
their respective permitted successors and assigns. Any assignment by the Company
or the Trust in contravention of such provisions will be null and void.

                                       8
<PAGE>

            Section 2.18 Miscellaneous Expenses.

      If at any time the Trust shall be required to pay any taxes, duties,
assessments or governmental charges of whatever nature (other than withholding
taxes) imposed by the United States, or any other domestic taxing authority,
then, in any such case, the Company agrees to pay, as additional interest
("Additional Sums"), such additional amounts as shall be required so that the
net amounts received and retained by the Trust with respect to the Securities
after paying any such taxes, duties, assessments or other governmental charges,
as well as all liabilities, costs and expenses of the Trust with respect to any
such items, will be not less than the amounts the Trust would have received had
no such taxes, duties, assessments or other governmental charges been imposed
and no such liabilities, costs and expenses with respect thereto been incurred.

                                  ARTICLE III

                            MISCELLANEOUS PROVISIONS

            Section 3.1 Adoption of the Supplemental Indenture. The Indenture,
as supplemented and amended by this Supplemental Indenture No. 1, is in all
respects hereby adopted, ratified and confirmed.

            Section 3.2 Counterparts. This Supplemental Indenture No. 1 may be
executed in any number of counterparts, each of which shall be an original, but
such counterparts shall together constitute but one and the same instrument.

            Section 3.3 Governing Law. THIS SUPPLEMENTAL INDENTURE NO. 1 AND
EACH SECURITY SHALL BE DEEMED TO BE A CONTRACT MADE UNDER THE LAWS OF THE STATE
OF NEW YORK AND SHALL BE GOVERNED AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF
THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW.

                                       9
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture No. 1 to be duly executed, as of the day and year first written above.

                                       W. R. BERKLEY CORPORATION

                                       By /s/ Eugene G. Ballard
                                          ------------------------------------
                                         Name: Eugene G. Ballard
                                         Title: Senior Vice President

                                       THE BANK OF NEW YORK,
                                           as Trustee

                                       By /s/ Stacey B. Poindexter
                                          ------------------------------------
                                         Name: Stacey B. Poindexter
                                         Title: Assistant Vice President

                                       10
<PAGE>

                    [FORM OF FACE OF SUBORDINATED DEBENTURE]

      THIS SUBORDINATED DEBENTURE IS REGISTERED IN THE NAME OF THE BANK OF NEW
YORK, AS PROPERTY TRUSTEE, AND MAY NOT BE TRANSFERRED, SOLD OR OTHERWISE
DISPOSED OF OTHER THAN AS PERMITTED IN THE SUPPLEMENTAL INDENTURE DATED AS OF
JULY 26, 2005, A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY.

      [IF THE DEBENTURE IS TO BE A GLOBAL SECURITY INSERT - This Subordinated
Debenture is Global Security within the meaning of the Indenture hereinafter
referred to and is registered in the name of a Depositary or a nominee of a
Depositary. This Subordinated Debenture is exchangeable for Subordinated
Debentures registered in the name of a person other than the Depositary or its
nominee only in the limited circumstances described in the Indenture, and no
transfer of this Subordinated Debenture (other than a transfer of this
Subordinated Debenture as a whole by the Depositary to a nominee of the
Depositary or by a nominee of the Depositary to the Depositary or another
nominee of the Depositary) may be registered except in limited circumstances.]

      Unless this Subordinated Debenture is presented by an authorized
representative of The Depository Trust Company (55 Water Street, New York, New
York) to the issuer or its agent for registration of transfer, exchange or
payment, and any Subordinated Debenture issued is registered in the name of Cede
& Co. or such other name as requested by an authorized representative of the
Depository Trust Company and any payment hereon is made to Cede & Co., ANY
TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY A PERSON IS
WRONGFUL since the registered owner hereof, Cede & Co., has an interest herein.

                            W.R. BERKLEY CORPORATION

CUSIP No.: 084423 AN 2

                6.750% Subordinated Debentures Due July 26, 2045

No.                                                                  $__________

      W. R. BERKLEY CORPORATION, a corporation duly organized and existing under
the laws of the State of Delaware (herein called the "Company", which term
includes any successor corporation under the Indenture (as defined on the
reverse hereof)), for value received, hereby promises to pay to___________, the
principal sum of $____________ Dollars on July 26, 2045 (such date is
hereinafter referred to as the "Stated Maturity") and to pay interest thereon
from July 26, 2005. Interest shall be payable on this Subordinated Debenture, in
arrears, on January 30, April 30, July 30 and October 30 of each year (each an
"Interest Payment Date") commencing October 30, 2005, at the rate of 6.750% per
annum, until the principal hereof is paid or made available for payment;
provided that any such installment of interest which is overdue shall bear
interest at the rate of 6.750% per annum (to the extent that the payment of such
interest shall be legally enforceable) from the dates such amounts are due until
they are paid or made available for payment, and such interest shall be payable
on demand; provided further

                                       A-1
<PAGE>

that, notwithstanding anything contained in the Indenture (as defined on the
reverse hereof) to the contrary, the Company shall have the right at any time,
and from time to time, during the term of this Subordinated Debenture to defer
payments of interest by extending the interest payment period to the next
Interest Payment Date by one or more quarterly periods not exceeding 20
consecutive quarters (each such period, an "Extension Period"), but no such
Extension Period may extend beyond July 26, 2045, or such other date to which
the Stated Maturity may have been shortened or extended as described below. At
the end of any such Extension Period, the Company shall pay all interest then
accrued and unpaid (including any Additional Sums, as defined in Section 2.18 of
Supplemental Indenture No. 1), together with interest thereon compounded
quarterly at the rate specified for this Subordinated Debenture to the extent
permitted by applicable law; provided, that during any such Extension Period,
(a) the Company shall not declare or pay dividends on, make any distribution
with respect to, or redeem, purchase, acquire or make a liquidation payment with
respect to any of its Capital Stock (other than (i) purchases or acquisitions of
shares of the Company's Common Stock in connection with the satisfaction by the
Company of its obligations under any employee benefit plans or the satisfaction
by the Company of its obligation pursuant to any contract or security requiring
it to purchase shares of its Common Stock, (ii) as a result of a
reclassification of the Company's Capital Stock or the exchange or conversion of
one class or series of the Company's Capital Stock for another class or series
of its Capital Stock, (iii) the purchase of fractional interests in shares of
the Company's Capital Stock pursuant to an acquisition or the conversion or
exchange provisions of such Capital Stock or the security being converted or
exchanged and (iv) redemptions or purchases pursuant to the Company's Rights
Agreement dated as of May 11, 1999, as amended, between the Company and Wells
Fargo Bank, N.A. as successor in interest to ChaseMellon Shareholder Services,
LLC, (b) the Company shall not make any payment of principal, premium, if any,
or interest on or repay, repurchase or redeem any debt securities issued by the
Company that rank pari passu with or junior to this Subordinated Debenture and
(c) the Company shall not make any guarantee payments with respect to the
foregoing (other than pursuant to the Preferred Securities Guarantee Agreement,
dated as of July 26, 2005, of the Company (the "Preferred Guarantee") with
respect to the 6.750% Trust Originated Preferred Securities (the "Preferred
Securities") issued by W. R. Berkley Capital Trust II (the "Trust"), the Common
Securities Guarantee Agreement, dated as of July 26, 2005, of the Company (the
"Common Guarantee" and together with the Preferred Guarantee, the "Guarantees")
with respect to the 6.750% Trust Originated Common Securities (the "Common
Securities" and together with the Preferred Securities, the "Trust Securities")
issued by the Trust and the Common Securities Guarantee Agreement, dated as of
December 20, 1996, and the Capital Securities Guarantee Agreement, dated as of
June 6, 1997 with respect to the 8.197% Capital Securities)). Prior to the
termination of any such Extension Period, the Company may further defer payments
of interest by extending the interest payment period; provided, however, that,
such Extension Period, including all such previous and further extensions, may
not exceed 20 consecutive quarters or extend beyond the Stated Maturity. Upon
the termination of any Extension Period and the payment of all amounts then due,
the Company may commence a new Extension Period, subject to the terms set forth
below. No interest shall be due and payable during any Extension Period, except
at the end thereof, but the Company may prepay at any time all or any portion of
the interest accrued during any Extension Period. If the Property Trustee (as
defined in the Amended and Restated Trust Agreement of the Trust (the "Trust
Agreement") shall be the sole holder of this Subordinated Debenture, Company
shall give the Administrative Trustees (as

                                       A-2
<PAGE>

defined in the Trust Agreement) and the Property Trustee (as defined in the
Trust Agreement), notice of its selection of such Extension Period one Business
Day prior to the earlier of (i) the date Distributions on the Preferred
Securities are payable or (ii) the date the Administrative Trustees are required
to give notice of the record date or the date such distribution is payable to
the New York Stock Exchange (or other applicable self-regulatory organization)
or to holders of the Preferred Securities, but in any event at least one
Business Day before such record date. If the Property Trustee shall not be the
sole holder of this Subordinated Debenture, the Company shall give the holders
of this Subordinated Debenture notice of its selection of such Extension Period
at least 10 Business Days prior to the earlier of (i) the Interest Payment Date
or (ii) the date upon which the Company is required to give notice of the record
or payment date of such interest payment to the New York Stock Exchange (or
other applicable self-regulatory organization) or to holders of this
Subordinated Debenture. The quarter in which any notice is given in accordance
with the foregoing provisions shall be counted as one of the 20 quarters
permitted in the maximum Extension Period permitted hereunder.

      The amount of interest payable on any Interest Payment Date shall be
computed on the basis of twelve 30-day months and a 360-day year and, for any
period that is shorter than a full 90-day quarter, will be calculated on the
basis of the actual number of days elapsed in such period. In the event that any
date on which interest is payable on this Subordinated Debenture is not a
Business Day, then payment of the interest payable on such date will be made on
the next succeeding day which is a Business Day (and without any interest or
other payment in respect of any such delay), except that, if such Business Day
is in the next succeeding calendar year, such payment shall be made on the
immediately preceding Business Day, in each case with the same force and effect
as if made on such date. The interest so payable on any Interest Payment Date
which is punctually paid or duly provided for on any Interest Payment Date will,
as provided in the Indenture referred to on the reverse hereof, be paid to the
person in whose name this Subordinated Debenture is registered at the close of
business on the Regular Record Date for such Interest Payment Date, which shall
be the Business Day preceding such Interest Payment Date; provided, that in the
event the Securities shall not continue to remain in book-entry only form, the
record dates shall be the January 15, April 15, July 15 and October 15 prior to
the applicable Interest Payment Date. Any such interest not so punctually paid
or duly provided for will forthwith cease to be payable to the Person in whose
name this Subordinated Debenture is registered on the relevant Regular Record
Date, and such defaulted interest shall instead be payable to the person in
whose name this Subordinated Debenture is registered on the special record date
for such defaulted interest or other specified date determined in accordance
with the Indenture and the Supplemental Indenture referred to on the reverse
hereof.

      Payment of the principal of and any such interest on this Subordinated
Debenture will be made at the Corporate Trust Office of the Trustee, in such
coin or currency of the United States of America as at the time of payment is
legal tender for payment of public and private debts, provided, however, that at
the option of the Company payment of interest may be paid (i) by check mailed to
the address of the person entitled thereto as such address shall appear in the
Security Register for Subordinated Debentures or (ii) by wire transfer to an
account maintained by the person entitled thereto as specified in such Register.

                                       A-3
<PAGE>

      Reference is hereby made to the further provisions of this Subordinated
Debenture set forth on the reverse hereof, which further provisions shall for
all purposes have the same effect as if set forth at this place.

      Unless the certificate of authentication hereon has been executed by the
Trustee referred to on the reverse hereof by manual signature, this Subordinated
Debenture shall not be entitled to any benefit under the Indenture and
Supplemental Indenture referred to on the reverse hereof or be valid or
obligatory for any purpose.

                                       A-4
<PAGE>

      IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

Dated:  July 26, 2005

                                       W. R. BERKLEY CORPORATION

                                       By_____________________________________
                                       Name:
                                       Title:

      This is one of the Securities of the series described in the
within-mentioned Indenture.

                                       THE BANK OF NEW YORK, as Trustee

                                       By:____________________________________
                                          Authorized Signatory

                                      A-5
<PAGE>

                   [FORM OF REVERSE OF SUBORDINATED DEBENTURE]

      This Subordinated Debenture is one of a duly authorized issue of
securities of the Company (herein called the "Securities"), issued and to be
issued in one or more series under a Subordinated Indenture, dated as of the
date hereof (herein, together with Supplemental Indenture No. 1 (as defined
below) called the "Indenture"), from the Company to The Bank of New York (herein
called the "Trustee", which term includes any successor trustee under the
Indenture), to which Indenture reference is hereby made for a statement of the
respective rights, limitations of rights, duties and immunities thereunder of
the Company, the Trustee, the holders of Senior Indebtedness and the Holders of
the Securities and of the terms upon which the Securities are, and are to be,
authenticated and delivered. This Security is one of the series designated on
the face hereof, limited in aggregate principal amount to $250,000,000 and is
issued pursuant to Supplemental Indenture No. 1, dated as of July 26, 2005, from
the Company to the Trustee, relating to the Securities of this series (herein
called "Supplemental Indenture No. 1").

      The indebtedness evidenced by this Security is to the extent provided in
the Indenture, subordinate and junior in right of payment to all Company Senior
Indebtedness, and this Security is issued subject to the provisions of the
Indenture with respect thereto. Each Holder of this Security, by accepting the
same, (a) agrees to and shall be bound by such provisions, (b) authorizes and
directs the Trustee on his behalf to take such action as may be necessary or
appropriate to acknowledge or effectuate the subordination so provided and (c)
appoints the Trustee his attorney-in-fact for any and all such purposes. Each
Holder hereof, by his acceptance hereof, hereby waives all notice of the
acceptance of the subordination provisions contained herein and in the Indenture
by each holder of Company Senior Indebtedness, whether now outstanding or
hereafter incurred, and waives reliance by each such holder upon said
provisions.

      The Securities of this series are subject to redemption at any time in
whole or from time to time in part, on or after July 26, 2010, but prior to
their Stated Maturity, upon not less than 30 nor more than 60 days' notice, at a
redemption price equal to 100% of the principal amount of the Securities to be
redeemed plus any accrued and unpaid interest, including Additional Sums (as
defined in Section 2.18 of Supplemental Indenture No. 1), if any, to the date
fixed for redemption (the "Redemption Price").

      The Company will have the right at any time to dissolve the Trust and
cause the Securities to be distributed to the holders of the Trust Securities in
accordance with the Trust Agreement.

      If, at any time, a Tax Event or an Investment Company Event (each a
"Special Event") has occurred and is continuing, the Company shall have the
right, upon not less than 30 nor more than 60 days notice, to redeem the
Securities in whole but not in part, for cash in the amount of the Redemption
Price, within 90 days following the occurrence of such Special Event, and,
following such redemption, Trust Securities with an aggregate liquidation amount
equal to the aggregate principal amount of the Securities so redeemed shall be
redeemed by the Trust at the Redemption Price; provided, however, that if at the
time there is available to the Company or the

                                      A-6
<PAGE>

Trust the opportunity to eliminate, within such 90-day period, the Tax Event by
taking some ministerial action, such as filing a form or making an election or
pursuing some other similar reasonable measure that has no adverse effect on the
Trust, the Company or the holders of the Trust Securities, the Company or the
Trust will pursue such measure in lieu of a redemption. If the Company does not
elect either to distribute the Securities to the holders of the Preferred
Securities in liquidation of the Trust or to redeem the Securities, the Trust
Securities shall remain outstanding and, in the event a Special Event is
continuing, Additional Sums (as defined in Section 10.9 of the Indenture) will
be payable on the Securities.

      In the event of redemption of this Security in part only, a new Security
or Securities of this series and of like tenor for the unredeemed portion hereof
will be issued in the name of the Holder hereof upon the cancellation hereof.

      If an Event of Default with respect to Securities of this series shall
occur and be continuing, the principal of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the
Indenture.

      The Indenture contains provisions for defeasance at any time of the
indebtedness of this Security or of certain restrictive covenants and Events of
Default with respect to this Security, in each case upon compliance by the
Company with certain conditions set forth therein, which provisions apply to
this Security.

      The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each series to be
affected under the Indenture at any time by the Company and the Trustee with the
consent of the Holders of at least a majority in aggregate principal amount of
the Securities at the time Outstanding of each series to be affected. The
Indenture also contains provisions permitting the Holders of specified
percentages in principal amount of the Securities of each series at the time
Outstanding, on behalf of the Holders of all Securities of such series, to waive
compliance by the Company with certain provisions of the Indenture and certain
past defaults under the Indenture and their consequences. Any such consent or
waiver by the Holder of the Security shall be conclusive and binding upon such
Holder and upon all future Holders of this Security and of any Security issued
upon the registration of transfer hereof or in exchange herefor or in lieu
hereof, whether or not notation of such consent or waiver is made upon this
Security.

      No reference herein to the Indenture or to Supplemental Indenture No. 1
and no provision of this Security or of the Indenture or Supplemental Indenture
No. 1 shall alter or impair the obligation of the Company, which is absolute and
unconditional, to pay the principal of, and interest on, this Security at the
times, place and rate, and in the coin or currency, herein prescribed.

      As provided in the Indenture and subject to certain limitations as therein
set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for registration of transfer at the
office or agency of the Company in any place where the principal of and interest
on this Security are payable, duly endorsed by, or accompanied by a written
instrument of transfer in form satisfactory to the Company, the Trustee and the
Registrar duly

                                      A-7
<PAGE>

executed by the Holder hereof or his attorney duly authorized in writing, and
thereupon one or more new Securities of this series and of like tenor, of
authorized denominations and for the same aggregate principal amount, will be
issued to the designated transferee or transferees.

      The Securities of this series are issuable only in registered form without
coupons in denominations of $1,000 and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations therein set forth,
Securities of this series are exchangeable for a like aggregate principal amount
of Securities of this series of like tenor of a different authorized
denomination, as requested by the Holder surrendering the same.

      No service charge shall be made for any such registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

      Prior to due presentment of this Security for registration of transfer,
the Company, the Trustee and any agent of the Company or the Trustee may treat
the person in whose name this Security is registered as the owner hereof for all
purposes, whether or not the Security be overdue, and neither the Company, the
Trustee nor any such agent shall be affected by notice to the contrary.

      The Company and the Holder of this Security agree (i) that for United
States federal, state and local tax purposes it is intended that this Security
constitute indebtedness and (ii) to file all United States federal, state and
local tax returns and reports on such basis (unless the Company or such Holder,
as the case may be, shall have received an opinion of independent nationally
recognized tax counsel to the effect that as a result of a change in law after
the date of the issuance of this Security the Company or such Holder, as the
case may be, is prohibited from filing on such basis).

      All terms used in this Security which are defined in the Indenture shall
have the meanings assigned to them in the Indenture.

                                      A-8<PAGE>

                                                                    Exhibit 4.6

================================================================================

                    PREFERRED SECURITIES GUARANTEE AGREEMENT

                                       by

                           W. R. BERKLEY CORPORATION,
                                  as Guarantor

                                   relating to

                         W. R. BERKLEY CAPITAL TRUST II

                            Dated as of July 26, 2005

================================================================================

<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>

                                                                                          Page
                                                                                          ----
<S>                                                                                       <C>
ARTICLE I.      DEFINITIONS AND INTERPRETATION..........................................    1

Section 1.1.    Definitions and Interpretation..........................................    1

ARTICLE II.     TRUST INDENTURE ACT.....................................................    4

Section 2.1.    Trust Indenture Act; Application........................................    4
Section 2.2.    Lists of Holders of Securities..........................................    4
Section 2.3.    Reports by the Preferred Guarantee Trustee..............................    5
Section 2.4.    Periodic Reports to Preferred Guarantee Trustee.........................    5
Section 2.5.    Evidence of Compliance with Conditions Precedent........................    5
Section 2.6.    Events of Default; Waiver...............................................    5
Section 2.7.    Event of Default; Notice................................................    5
Section 2.8.    Conflicting Interests...................................................    6

ARTICLE III.    POWERS, DUTIES AND RIGHTS OF PREFERRED GUARANTEE TRUSTEE................    6

Section 3.1.    Powers and Duties of the Preferred Guarantee Trustee....................    6
Section 3.2.    Certain Rights of Preferred Guarantee Trustee...........................    8
Section 3.3.    Not Responsible for Recitals or Issuance of Guarantee...................    9

ARTICLE IV.     PREFERRED GUARANTEE TRUSTEE.............................................   10

Section 4.1.    Preferred Guarantee Trustee; Eligibility................................   10
Section 4.2.    Appointment, Removal and Resignation of Preferred Guarantee Trustees....   10

ARTICLE V.      GUARANTEE...............................................................   11

Section 5.1.    Guarantee...............................................................   11
Section 5.2.    Waiver of Notice and Demand.............................................   11
Section 5.3.    Obligations Not Affected................................................   11
Section 5.4.    Rights of Holders.......................................................   12
Section 5.5.    Guarantee of Payment....................................................   13
Section 5.6.    Subrogation.............................................................   13
Section 5.7.    Independent Obligations.................................................   13
Section 5.8.    Taxes...................................................................   13

ARTICLE VI.     LIMITATION OF TRANSACTIONS; SUBORDINATION...............................   13

Section 6.1.    Limitation of Transactions..............................................   13
Section 6.2.    Subordinated Ranking....................................................   14

ARTICLE VII.    TERMINATION.............................................................   14

Section 7.1.    Termination.............................................................   14

ARTICLE VIII.   INDEMNIFICATION.........................................................   15
</TABLE>

                                       i
<PAGE>

<TABLE>
<S>                                                                                       <C>
Section 8.1.    Exculpation.............................................................   15
Section 8.2.    Indemnification.........................................................   15

ARTICLE IX.     MISCELLANEOUS...........................................................   16

Section 9.1.    Successors and Assigns..................................................   16
Section 9.2.    Amendments..............................................................   16
Section 9.3.    Notices.................................................................   16
Section 9.4.    Benefit.................................................................   17
Section 9.5.    Governing Law...........................................................   17
</TABLE>

                                       ii
<PAGE>

                    PREFERRED SECURITIES GUARANTEE AGREEMENT

      This GUARANTEE AGREEMENT (the "Preferred Securities Guarantee"), dated as
of July 26, 2005, is executed and delivered by W. R. Berkley Corporation, a
Delaware corporation (the "Guarantor"), and The Bank of New York, a New York
corporation, as trustee (the "Preferred Guarantee Trustee"), for the benefit of
the Holders (as defined herein) from time to time of the Preferred Securities
(as defined herein) of W. R. Berkley Capital Trust II, a Delaware statutory
trust (the "Issuer").

      WHEREAS, pursuant to an Amended and Restated Trust Agreement (the "Trust
Agreement"), dated as of July 26, 2005, among the trustees of the Issuer named
therein, the Guarantor, as sponsor, and the holders from time to time of
undivided beneficial interests in the assets of the Issuer, the Issuer is
issuing on the date hereof 10,000,000 preferred securities, having an aggregate
liquidation amount of $250,000,000, designated the 6.750% Trust Originated
Preferred Securities (the "Preferred Securities") and four common securities,
having an aggregate liquidation amount of $100 designated the 6.750% Trust
Originated Common Securities (the "Common Securities");

      WHEREAS, as incentive for the Holders to purchase the Preferred
Securities, the Guarantor desires irrevocably and unconditionally to agree, to
the extent set forth in this Preferred Securities Guarantee, to pay to the
Holders of the Preferred Securities the Guarantee Payments (as defined herein)
and to make certain other payments on the terms and conditions set forth herein;
and

      WHEREAS, the Guarantor is also executing and delivering a guarantee
agreement (the "Common Securities Guarantee") in substantially identical terms
to this Preferred Securities Guarantee for the benefit of the holders of the
Common Securities (as defined herein), except that if an Event of Default (as
defined in the Indenture), has occurred and is continuing, the rights of holders
of the Common Securities to receive Guarantee Payments under the Common
Securities Guarantee are subordinated to the rights of Holders of Preferred
Securities to receive Guarantee Payments under this Preferred Securities
Guarantee.

      NOW, THEREFORE, in consideration of the purchase by each Holder of
Preferred Securities, which purchase the Guarantor hereby agrees shall benefit
the Guarantor, the Guarantor executes and delivers this Preferred Securities
Guarantee for the benefit of the Holders.

                                   ARTICLE I.
                         DEFINITIONS AND INTERPRETATION

      Section 1.1. Definitions and Interpretation. In this Preferred Securities
Guarantee, unless the context otherwise requires:

            (a) Capitalized terms used in this Preferred Securities Guarantee
      but not defined in the preamble above have the respective meanings
      assigned to them in this Section 1.1;

                                       1
<PAGE>

            (b) a term defined anywhere in this Preferred Securities Guarantee
      has the same meaning throughout;

            (c) all references to "the Preferred Securities Guarantee" or "this
      Preferred Securities Guarantee" are to this Preferred Securities Guarantee
      as modified, supplemented or amended from time to time;

            (d) all references in this Preferred Securities Guarantee to
      Articles and Sections are to Articles and Sections of this Preferred
      Securities Guarantee, unless otherwise specified;

            (e) a term defined in the Trust Indenture Act has the same meaning
      when used in this Preferred Securities Guarantee, unless otherwise defined
      in this Preferred Securities Guarantee or unless the context otherwise
      requires; and

            (f) a reference to the singular includes the plural and vice versa.

      "Affiliate" has the same meaning as given to that term in Rule 405 of the
Securities Act of 1933, as amended, or any successor rule thereunder.

      "Authorized Officer" of a Person means any Person that is authorized to
bind such Person.

      "Business Day" means any day other than a day on which banking
institutions in New York, New York or Wilmington, Delaware, are authorized or
required by law or executive order to close.

      "Common Securities" means the securities representing common undivided
beneficial interests in the assets of the Issuer.

      "Corporate Trust Office" means the office of the Preferred Guarantee
Trustee at which the corporate trust business of the Preferred Guarantee Trustee
shall, at any particular time, be principally administered, which office at the
date of execution of this Agreement is located at The Bank of New York, 101
Barclay Street, 8W, New York, New York 10286, Attention: Geovanni Barris.

      "Covered Person" means any Holder or beneficial owner of Preferred
Securities.

      "Debentures" means the series of junior subordinated debt securities of
the Guarantor designated the 6.750% Subordinated Debentures due 2045, held by
the Property Trustee (as defined in the Trust Agreement) of the Issuer.

      "Event of Default" means a default by the Guarantor on any of its payment
or other obligations under this Preferred Securities Guarantee.

      "Guarantee Payments" means the following payments or distributions,
without duplication, with respect to the Preferred Securities, to the extent not
paid or made by the Issuer: (i) any accrued and unpaid Distributions (as defined
in the Trust Agreement) that are required to

                                       2
<PAGE>

be paid on such Preferred Securities to the extent the Issuer shall have funds
available therefor at such time, (ii) the redemption price, including all
accrued and unpaid Distributions to the date of redemption (the "Redemption
Price") to the extent the Issuer has funds available therefor at such time, with
respect to any Preferred Securities called for redemption, and (iii) upon a
voluntary or involuntary dissolution, winding-up or termination of the Issuer
(other than in connection with the distribution of Debentures to the Holders),
the lesser of (a) the aggregate of the liquidation amount and all accrued and
unpaid Distributions on the Preferred Securities to the date of payment, to the
extent the Issuer shall have funds available therefor at such time, and (b) the
amount of assets of the Issuer remaining available at such time for distribution
to Holders in liquidation of the Issuer (in either case, the "Liquidation
Distribution"). If an event of default under the Indenture has occurred and is
continuing, the rights of holders of the Common Securities to receive payments
under the Common Securities Guarantee Agreement are subordinated to the rights
of Holders of Preferred Securities to receive Guarantee Payments.

      "Holder" shall mean any holder, as registered on the books and records of
the Issuer of any Preferred Securities; provided, however, that, in determining
whether the holders of the requisite percentage of Preferred Securities have
given any request, notice, consent or waiver hereunder, "Holder" shall not
include the Guarantor or any Affiliate of the Guarantor.

      "Indemnified Person" means the Preferred Guarantee Trustee, any Affiliate
of the Preferred Guarantee Trustee, or any officers, directors, shareholders,
members, partners, employees, representatives, nominees, custodians or agents of
the Preferred Guarantee Trustee.

      "Indenture" means the Subordinated Indenture dated as of July 26, 2005,
among the Guarantor (the "Debenture Issuer") and The Bank of New York, as
trustee, and any indenture supplemental thereto pursuant to which certain
subordinated debt securities of the Debenture Issuer are to be issued to the
Property Trustee of the Issuer.

      "Majority in liquidation amount of the Securities" means, except as
provided by the Trust Indenture Act, a vote by Holder(s) of Preferred
Securities, voting separately as a class, of more than 50% of the liquidation
amount (including the stated amount that would be paid on redemption,
liquidation or otherwise, plus accrued and unpaid Distributions to the date upon
which the voting percentages are determined) of all Preferred Securities.

      "Officers' Certificate" means, with respect to any Person, a certificate
signed by two Authorized Officers of such Person. Any Officers' Certificate
delivered with respect to compliance with a condition or covenant provided for
in this Preferred Securities Guarantee shall include:

            (a) a statement that each officer signing the Officers' Certificate
      has read the covenant or condition and the definition relating thereto;

            (b) a brief statement of the nature and scope of the examination or
      investigation undertaken by each officer in rendering the Officers'
      Certificate;

            (c) a statement that each such officer has made such examination or
      investigation as, in such officer's opinion, is necessary to enable such
      officer to express

                                       3
<PAGE>

      an informed opinion as to whether or not such covenant or condition has
      been complied with; and

            (d) a statement as to whether, in the opinion of each such officer,
      such condition or covenant has been complied with.

      "Person" means a legal person, including any individual, corporation,
estate, partnership, joint venture, association, joint stock company, limited
liability company, trust, unincorporated association, or government or any
agency or political subdivision thereof, or any other entity of whatever nature.

      "Preferred Guarantee Trustee" means The Bank of New York until a Successor
Preferred Guarantee Trustee has been appointed and has accepted such appointment
pursuant to the terms of this Preferred Securities Guarantee and thereafter
means each such Successor Preferred Guarantee Trustee.

      "Responsible Officer" means, with respect to the Preferred Guarantee
Trustee, any officer within the Corporate Trust Office of the Preferred
Guarantee Trustee, including any vice-president, any assistant vice-president,
any assistant secretary, the treasurer, any assistant treasurer or other officer
of the Corporate Trust Office of the Preferred Guarantee Trustee customarily
performing functions similar to those performed by any of the above designated
officers and also means, with respect to a particular corporate trust matter,
any other officer to whom such matter is referred because of that officer's
knowledge of and familiarity with the particular subject.

      "Successor Preferred Guarantee Trustee" means a successor Preferred
Guarantee Trustee possessing the qualifications to act as Preferred Guarantee
Trustee under Section 4.1.

      "Trust Indenture Act" means the Trust Indenture Act of 1939, as amended.

                                  ARTICLE II.

                               TRUST INDENTURE ACT

      Section 2.1.Trust Indenture Act; Application.

            (a) This Preferred Securities Guarantee is subject to the provisions
      of the Trust Indenture Act that are required to be part of this Preferred
      Securities Guarantee and shall, to the extent applicable, be governed by
      such provisions; and

            (b) if and to the extent that any provision of this Preferred
      Securities Guarantee limits, qualifies or conflicts with the duties
      imposed by Section 310 to 317, inclusive, of the Trust Indenture Act, such
      imposed duties shall control.

      Section 2.2. Lists of Holders of Securities.

            (a) The Guarantor shall provide the Preferred Guarantee Trustee with
      a list, in such form as the Preferred Guarantee Trustee may reasonably
      require, of the names and

                                       4
<PAGE>

      addresses of the Holders of the Preferred Securities ("List of Holders")
      as of such date, (i) concurrently with the provision of such a list to the
      Property Trustee pursuant to the Trust Agreement, and (ii) at any time
      within 30 days of receipt by the Guarantor of a written request for a List
      of Holders as of a date no more than 14 days before such List of Holders
      is given to the Preferred Guarantee Trustee provided, that the Guarantor
      shall not be obligated to provide such List of Holders at any time the
      List of Holders does not differ from the most recent List of Holders given
      to the Preferred Guarantee Trustee by the Guarantor. The Preferred
      Guarantee Trustee may destroy any List of Holders previously given to it
      on receipt of a new List of Holders.

            (b) The Preferred Guarantee Trustee shall comply with its
      obligations under Section 311(a), 311(b) and Section 312(b) of the Trust
      Indenture Act.

      Section 2.3.Reports by the Preferred Guarantee Trustee. Within 60 days
after May 15 of each year, the Preferred Guarantee Trustee shall provide to the
Holders of the Preferred Securities such reports as are required by Section 313
of the Trust Indenture Act, if any, in the form and in the manner provided by
Section 313 of the Trust Indenture Act. The Preferred Guarantee Trustee shall
also comply with the requirements of Section 313(d) of the Trust Indenture Act.

      Section 2.4.Periodic Reports to Preferred Guarantee Trustee. The Guarantor
shall provide to the Preferred Guarantee Trustee such documents, reports and
information as required by Section 314 (if any) and the compliance certificate
required by Section 314 of the Trust Indenture Act in the form, in the manner
and at the times required by Section 314 of the Trust Indenture Act.

      Section 2.5.Evidence of Compliance with Conditions Precedent. The
Guarantor shall provide to the Preferred Guarantee Trustee such evidence of
compliance with any conditions precedent, if any, provided for in this Preferred
Securities Guarantee that relate to any of the matters set forth in Section
314(c) of the Trust Indenture Act. Any certificate or opinion required to be
given by an officer pursuant to Section 314(c)(1) may be given in the form of an
Officers' Certificate.

      Section 2.6.Events of Default; Waiver. The Holders of a Majority in
liquidation amount of Preferred Securities may, by vote, on behalf of the
Holders of all of the Preferred Securities, waive any past Event of Default and
its consequences except as provided for in Section 2.6 of the Trust Agreement
and Section 5.13 of the Indenture. Upon such waiver, any such Event of Default
shall cease to exist, and any Event of Default arising therefrom shall be deemed
to have been cured, for every purpose of this Preferred Securities Guarantee,
but no such waiver shall extend to any subsequent or other default or Event of
Default or impair any right consequent thereon.

      Section 2.7.Event of Default; Notice.

            (a) The Preferred Guarantee Trustee shall, within five (5) Business
      Days after the occurrence of an Event of Default, transmit by mail, first
      class postage prepaid, to the Holders of the Preferred Securities, notices
      of all Events of Default actually known to a

                                       5
<PAGE>

      Responsible Officer of the Preferred Guarantee Trustee, unless such
      defaults have been cured before the giving of such notice, provided, that,
      the Preferred Guarantee Trustee shall be protected in withholding such
      notice if and so long as a Responsible Officer of the Preferred Guarantee
      Trustee in good faith determines that the withholding of such notice is in
      the interests of the Holders of the Preferred Securities.

            (b) The Preferred Guarantee Trustee shall not be deemed to have
      knowledge of any Event of Default unless the Preferred Guarantee Trustee
      shall have received written notice of such Event of Default, or unless a
      Responsible Officer of the Preferred Guarantee Trustee charged with the
      administration of the Trust Agreement shall have obtained actual knowledge
      thereof.

      Section 2.8.Conflicting Interests. The Trust Agreement shall be deemed to
be specifically described in this Preferred Securities Guarantee for the
purposes of clause (i) of the first proviso contained in Section 310(b) of the
Trust Indenture Act.

                                  ARTICLE III.

                          POWERS, DUTIES AND RIGHTS OF
                           PREFERRED GUARANTEE TRUSTEE

      Section 3.1. Powers and Duties of the Preferred Guarantee Trustee.

            (a) This Preferred Securities Guarantee shall be held by the
      Preferred Guarantee Trustee for the benefit of the Holders of the
      Preferred Securities, and the Preferred Guarantee Trustee shall not
      transfer this Preferred Securities Guarantee to any Person except a Holder
      of Preferred Securities exercising his or her rights pursuant to Section
      5.4(b) or to a Successor Preferred Guarantee Trustee on acceptance by such
      Successor Preferred Guarantee Trustee of its appointment to act as
      Successor Preferred Guarantee Trustee. The right, title and interest of
      the Preferred Guarantee Trustee shall automatically vest in any Successor
      Preferred Guarantee Trustee, and such vesting and cessation of title shall
      be effective whether or not conveyancing documents have been executed and
      delivered pursuant to the appointment of such Successor Preferred
      Guarantee Trustee.

            (b) If an Event of Default actually known to a Responsible Officer
      of the Preferred Guarantee Trustee has occurred and is continuing, the
      Preferred Guarantee Trustee shall enforce this Preferred Securities
      Guarantee for the benefit of the Holders of the Preferred Securities.

            (c) The Preferred Guarantee Trustee, before the occurrence of any
      Event of Default and after the curing or waiver of all Events of Default
      that may have occurred, shall undertake to perform only such duties as are
      specifically set forth in this Preferred Securities Guarantee, and no
      implied covenants or obligations shall be read into this Preferred
      Securities Guarantee against the Preferred Guarantee Trustee. In case an
      Event of Default has occurred (that has not been cured or waived pursuant
      to Section 2.6) and is actually known to a Responsible Officer of the
      Preferred Guarantee Trustee, the Preferred

                                       6
<PAGE>

      Guarantee Trustee shall exercise such of the rights and powers vested in
      it by this Preferred Securities Guarantee, and shall use the same degree
      of care and skill in its exercise thereof, as a prudent person would
      exercise or use under the circumstances in the conduct of his or her own
      affairs.

            (d) No provision of this Preferred Securities Guarantee shall be
      construed to relieve the Preferred Guarantee Trustee from liability for
      its own negligent action, its own negligent failure to act, or its own
      willful misconduct, except that:

                  (i) prior to the occurrence of any Event of Default and after
            the curing or waiving of all such Events of Default that may have
            occurred:

                        (A) the duties and obligations of the Preferred
                  Guarantee Trustee shall be determined solely by the express
                  provisions of this Preferred Securities Guarantee, and the
                  Preferred Guarantee Trustee shall not be liable except for the
                  performance of such duties and obligations as are specifically
                  set forth in this Preferred Securities Guarantee, and no
                  implied covenants or obligations shall be read into this
                  Preferred Securities Guarantee against the Preferred Guarantee
                  Trustee; and

                        (B) in the absence of bad faith on the part of the
                  Preferred Guarantee Trustee, the Preferred Guarantee Trustee
                  may conclusively rely, as to the truth of the statements and
                  the correctness of the opinions expressed therein, upon any
                  certificates or opinions furnished to the Preferred Guarantee
                  Trustee and conforming to the requirements of this Preferred
                  Securities Guarantee; but in the case of any such certificates
                  or opinions that by any provision hereof are specifically
                  required to be furnished to the Preferred Guarantee Trustee,
                  the Preferred Guarantee Trustee shall be under a duty to
                  examine the same to determine whether or not they conform to
                  the requirements of this Preferred Securities Guarantee;

                  (ii) the Preferred Guarantee Trustee shall not be liable for
            any error of judgment made in good faith by a Responsible Officer of
            the Preferred Guarantee Trustee, unless it shall be proved that the
            Preferred Guarantee Trustee was negligent in ascertaining the
            pertinent facts upon which such judgment was made;

                  (iii) the Preferred Guarantee Trustee shall not be liable with
            respect to any action taken or omitted to be taken by it in good
            faith in accordance with the direction of the Holders of not less
            than a Majority in liquidation amount of the Preferred Securities
            relating to the time, method and place of conducting any proceeding
            for any remedy available to the Preferred Guarantee Trustee, or
            exercising any trust or power conferred upon the Preferred Guarantee
            Trustee under this Preferred Securities Guarantee; and

                  (iv) no provision of this Preferred Securities Guarantee shall
            require the Preferred Guarantee Trustee to expend or risk its own
            funds or otherwise incur personal financial liability in the
            performance of any of its duties or in the

                                       7
<PAGE>

            exercise of any of its rights or powers, if the Preferred Guarantee
            Trustee shall have reasonable grounds for believing that the
            repayment of such funds or liability is not reasonably assured to it
            under the terms of this Preferred Securities Guarantee or indemnity,
            reasonably satisfactory to the Preferred Guarantee Trustee, against
            such risk or liability is not reasonably assured to it.

      Section 3.2.Certain Rights of Preferred Guarantee Trustee. Subject to the
provisions of Section 3.1:

            (a) The Preferred Guarantee Trustee may conclusively rely, and shall
      be fully protected in acting or refraining from acting upon, any
      resolution, certificate, statement, instrument, opinion, report, notice,
      request, direction, consent, order, bond, debenture, note, other evidence
      of indebtedness or other paper or document believed by it to be genuine
      and to have been signed, sent or presented by the proper party or parties.

            (b) Any direction or act of the Guarantor contemplated by this
      Preferred Securities Guarantee shall be sufficiently evidenced by a
      Direction (as defined in the Trust Agreement) or an Officers' Certificate.

            (c) Whenever, in the administration of this Preferred Securities
      Guarantee, the Preferred Guarantee Trustee shall deem it desirable that a
      matter be proved or established before taking, suffering or omitting any
      action hereunder, the Preferred Guarantee Trustee (unless other evidence
      is herein specifically prescribed) may, in the absence of bad faith on its
      part, request and conclusively rely upon an Officers' Certificate which,
      upon receipt of such request, shall be promptly delivered by the
      Guarantor.

            (d) The Preferred Guarantee Trustee shall have no duty to see to any
      recording, filing or registration of any instrument (or any rerecording,
      refiling or registration thereof).

            (e) The Preferred Guarantee Trustee may consult with counsel, and
      the written advice or opinion of such counsel with respect to legal
      matters shall be full and complete authorization and protection in respect
      of any action taken, suffered or omitted by it hereunder in good faith and
      in accordance with such advice or opinion. Such counsel may be counsel to
      the Guarantor or any of its Affiliates and may include any of its
      employees. The Preferred Guarantee Trustee shall have the right at any
      time to seek instructions concerning the administration of this Preferred
      Securities Guarantee from any court of competent jurisdiction.

            (f) The Preferred Guarantee Trustee shall be under no obligation to
      exercise any of the rights or powers vested in it by this Preferred
      Securities Guarantee at the request or direction of any Holder, unless
      such Holder shall have provided to the Preferred Guarantee Trustee such
      security and indemnity, reasonably satisfactory to the Preferred Guarantee
      Trustee, against the costs, expenses (including attorneys' fees and
      expenses and the expenses of the Preferred Guarantee Trustee's agents,
      nominees or custodians) and liabilities that might be incurred by it in
      complying with such request or direction, including such reasonable
      advances as may be requested by the Preferred

                                       8
<PAGE>

      Guarantee Trustee; provided that, nothing contained in this Section 3.2(f)
      shall be taken to relieve the Preferred Guarantee Trustee, upon the
      occurrence of an Event of Default, of its obligation to exercise the
      rights and powers vested in it by this Preferred Securities Guarantee.

            (g) The Preferred Guarantee Trustee shall not be bound to make any
      investigation into the facts or matters stated in any resolution,
      certificate, statement, instrument, opinion, report, notice, request,
      direction, consent, order, bond, debenture, note, other evidence of
      indebtedness or other paper or document, but the Preferred Guarantee
      Trustee, in its discretion, may make such further inquiry or investigation
      into such facts or matters as it may see fit, but shall incur no liability
      of any kind by reason of such inquiry or investigation.

            (h) The Preferred Guarantee Trustee may execute any of the trusts or
      powers hereunder or perform any duties hereunder either directly or by or
      through agents, nominees, custodians or attorneys, and the Preferred
      Guarantee Trustee shall not be responsible for any misconduct or
      negligence on the part of any agent or attorney appointed with due care by
      it hereunder.

            (i) Any action taken by the Preferred Guarantee Trustee or its
      agents hereunder shall bind the Holders of the Preferred Securities, and
      the signature of the Preferred Guarantee Trustee or its agents alone shall
      be sufficient and effective to perform any such action. No third party
      shall be required to inquire as to the authority of the Preferred
      Guarantee Trustee to so act or as to its compliance with any of the terms
      and provisions of this Preferred Securities Guarantee, both of which shall
      be conclusively evidenced by the Preferred Guarantee Trustee's or its
      agent's taking such action.

            (j) Whenever in the administration of this Preferred Securities
      Guarantee the Preferred Guarantee Trustee shall deem it desirable to
      receive instructions with respect to enforcing any remedy or right or
      taking any other action hereunder, the Preferred Guarantee Trustee (i) may
      request instructions from the Holders of a Majority in liquidation amount
      of the Preferred Securities, (ii) may refrain from enforcing such remedy
      or right or taking such other action until such instructions are received,
      and (iii) shall be protected in conclusively relying on or acting in
      accordance with such instructions.

            (k) No provision of this Preferred Securities Guarantee shall be
      deemed to impose any duty or obligation on the Preferred Guarantee Trustee
      to perform any act or acts or exercise any right, power, duty or
      obligation conferred or imposed on it in any jurisdiction in which it
      shall be illegal, or in which the Preferred Guarantee Trustee shall be
      unqualified or incompetent in accordance with applicable law, to perform
      any such act or acts or to exercise any such right, power, duty or
      obligation. No permissive power or authority available to the Preferred
      Guarantee Trustee shall be construed to be a duty.

      Section 3.3. Not Responsible for Recitals or Issuance of Guarantee. The
recitals contained in this Guarantee shall be taken as the statements of the
Guarantor, and the Preferred Guarantee Trustee does not assume any
responsibility for their correctness. The Preferred

                                       9
<PAGE>

Guarantee Trustee makes no representation as to the validity or sufficiency of
this Preferred Securities Guarantee.

                                  ARTICLE IV.

                           PREFERRED GUARANTEE TRUSTEE

      Section 4.1. Preferred Guarantee Trustee; Eligibility.

            (a) There shall at all times be a Preferred Guarantee Trustee which
      shall:

                  (i) not be an Affiliate of the Guarantor; and

                  (ii) be a corporation organized and doing business under the
            laws of the United States of America or any State or Territory
            thereof or of the District of Columbia, or a corporation or Person
            permitted by the Securities and Exchange Commission to act as an
            institutional trustee under the Trust Indenture Act, authorized
            under such laws to exercise corporate trust powers, having a
            combined capital and surplus of at least 50 million U.S. dollars
            ($50,000,000), and subject to supervision or examination by Federal,
            State, Territorial or District of Columbia authority. If such
            corporation publishes reports of condition at least annually,
            pursuant to law or to the requirements of the supervising or
            examining authority referred to above, then, for the purposes of
            this Section 4.1(a)(ii), the combined capital and surplus of such
            corporation shall be deemed to be its combined capital and surplus
            as set forth in its most recent report of condition so published.

            (b) If at any time the Preferred Guarantee Trustee shall cease to be
      eligible to so act under Section 4.1(a), the Preferred Guarantee Trustee
      shall immediately resign in the manner and with the effect set out in
      Section 4.2 (c).

            (c) If the Preferred Guarantee Trustee has or shall acquire any
      "conflicting interest" within the meaning of Section 310(b) of the Trust
      Indenture Act, the Preferred Guarantee Trustee and Guarantor shall in all
      respects comply with the provisions of Section 310(b) of the Trust
      Indenture Act.

      Section 4.2. Appointment, Removal and Resignation of Preferred Guarantee
Trustees.

            (a) Subject to Section 4.2(b), the Preferred Guarantee Trustee may
      be appointed or removed without cause at any time by the Guarantor.

            (b) The Preferred Guarantee Trustee shall not be removed in
      accordance with Section 4.2(a) until a Successor Preferred Guarantee
      Trustee has been appointed and has accepted such appointment by written
      instrument executed by such Successor Preferred Guarantee Trustee and
      delivered to the Guarantor.

            (c) The Preferred Guarantee Trustee appointed to office shall hold
      office until a Successor Preferred Guarantee Trustee shall have been
      appointed or until its removal or resignation. The Preferred Guarantee
      Trustee may resign from office (without need for

                                       10
<PAGE>

      prior or subsequent accounting) by an instrument in writing executed by
      the Preferred Guarantee Trustee and delivered to the Guarantor, which
      resignation shall not take effect until a Successor Preferred Guarantee
      Trustee has been appointed and has accepted such appointment by instrument
      in writing executed by such Successor Preferred Guarantee Trustee and
      delivered to the Guarantor and the Preferred Guarantee Trustee.

            (d) If no Successor Preferred Guarantee Trustee shall have been
      appointed and accepted appointment as provided in this Section 4.2 within
      60 days after delivery to the Guarantor of an instrument of resignation or
      removal, the Preferred Guarantee Trustee resigning or being removed may
      petition any court of competent jurisdiction for appointment of a
      Successor Preferred Guarantee Trustee. Such court may thereupon, after
      prescribing such notice, if any, as it may deem proper, appoint a
      Successor Preferred Guarantee Trustee.

            (e) No Preferred Guarantee Trustee shall be liable for the acts or
      omissions to act of any Successor Preferred Guarantee Trustee.

            (f) Upon termination of this Preferred Securities Guarantee or
      removal or resignation of the Preferred Guarantee Trustee pursuant to this
      Section 4.2, the Guarantor shall pay to the Preferred Guarantee Trustee
      all amounts accrued to the date of such termination, removal or
      resignation.

                                   ARTICLE V.

                                    GUARANTEE

      Section 5.1. Guarantee. The Guarantor irrevocably and unconditionally
agrees to pay in full to the Holders the Guarantee Payments (without duplication
of amounts theretofore paid by the Issuer), as and when due, regardless of any
defense, right of set-off or counterclaim that the Issuer may have or assert.
The Guarantor's obligation to make a Guarantee Payment may be satisfied by
direct payment of the required amounts by the Guarantor to the Holders or by
causing the Issuer to pay such amounts to the Holders.

      Section 5.2. Waiver of Notice and Demand. The Guarantor hereby waives
notice of acceptance of this Preferred Securities Guarantee and of any liability
to which it applies or may apply, presentment, demand for payment, any right to
require a proceeding first against the Issuer or any other Person before
proceeding against the Guarantor, protest, notice of nonpayment, notice of
dishonor, notice of redemption and all other notices and demands.

      Section 5.3. Obligations Not Affected. The obligations, covenants,
agreements and duties of the Guarantor under this Preferred Securities Guarantee
shall in no way be affected or impaired by reason of the happening from time to
time of any of the following:

            (a) the release or waiver, by operation of law or otherwise, of the
      performance or observance by the Issuer of any express or implied
      agreement, covenant, term or condition relating to the Preferred
      Securities to be performed or observed by the Issuer;

                                       11
<PAGE>

            (b) the extension of time for the payment by the Issuer of all or
      any portion of the Distributions, Redemption Price, Liquidation
      Distribution or any other sums payable under the terms of the Preferred
      Securities or the extension of time for the performance of any other
      obligation under, arising out of, or in connection with, the Preferred
      Securities (other than an extension of time for payment of Distributions,
      Redemption Price, Liquidation Distribution or other sum payable that
      results from the extension of any interest payment period on the
      Debentures or any extension of the maturity date of the Debentures
      permitted by the Indenture);

            (c) any failure, omission, delay or lack of diligence on the part of
      the Holders to enforce, assert or exercise any right, privilege, power or
      remedy conferred on the Holders pursuant to the terms of the Preferred
      Securities, or any action on the part of the Issuer granting indulgence or
      extension of any kind;

            (d) the voluntary or involuntary liquidation, dissolution, sale of
      any collateral, receivership, insolvency, bankruptcy, assignment for the
      benefit of creditors, reorganization, arrangement, composition or
      readjustment of debt of, or other similar proceedings affecting, the
      Issuer or any of the assets of the Issuer;

            (e) any invalidity of, or defect or deficiency in, the Preferred
      Securities;

            (f) the settlement or compromise of any obligation guaranteed hereby
      or hereby incurred; or

            (g) any other circumstance whatsoever that might otherwise
      constitute a legal or equitable discharge or defense of a guarantor, it
      being the intent of this Section 5.3 that the obligations of the Guarantor
      hereunder shall be absolute and unconditional under any and all
      circumstances.

      There shall be no obligation of the Holders to give notice to, or obtain
consent of, the Guarantor with respect to the happening of any of the foregoing.

      Section 5.4. Rights of Holders.

            (a) The Holders of a Majority in liquidation amount of the Preferred
      Securities have the right to direct the time, method and place of
      conducting of any proceeding for any remedy available to the Preferred
      Guarantee Trustee in respect of this Preferred Securities Guarantee or
      exercising any trust or power conferred upon the Preferred Guarantee
      Trustee under this Preferred Securities Guarantee.

            (b) If the Preferred Guarantee Trustee fails to enforce this
      Preferred Securities Guarantee with respect to the right of any Holders to
      receive any Guarantee Payment in accordance herewith, such Holders may
      directly institute a proceeding against the Guarantor for enforcement of
      the Preferred Security Guarantee for such payment. The Guarantor waives
      any right or remedy to require that any action be brought first against
      the Issuer or any other Person or entity before proceeding directly
      against the Guarantor.

                                       12
<PAGE>

      Section 5.5. Guarantee of Payment. This Preferred Securities Guarantee
creates a guarantee of payment and not of collection.

      Section 5.6. Subrogation. The Guarantor shall be subrogated to all (if
any) rights of the Holders of Preferred Securities against the Issuer in respect
of any amounts paid to such Holders by the Guarantor under this Preferred
Securities Guarantee; provided, however, that the Guarantor shall not (except to
the extent required by mandatory provisions of law) be entitled to enforce or
exercise any right that it may acquire by way of subrogation or any indemnity,
reimbursement or other agreement, in all cases as a result of payment under this
Preferred Securities Guarantee, if, at the time of any such payment, any amounts
are due and unpaid under this Preferred Securities Guarantee. If any amount
shall be paid to the Guarantor in violation of the preceding sentence, the
Guarantor agrees to hold such amount in trust for the Holders and to pay over
such amount to the Holders.

      Section 5.7. Independent Obligations. The Guarantor acknowledges that its
obligations hereunder are independent of the obligations of the Issuer with
respect to the Preferred Securities, and that the Guarantor shall be liable as
principal and as debtor hereunder to make Guarantee Payments pursuant to the
terms of this Preferred Securities Guarantee notwithstanding the occurrence of
any event referred to in subsections (a) through (g), inclusive, of Section 5.3
hereof.

      Section 5.8. Taxes. All payments in respect of the Guarantee Payments
(including interest accrued thereon, if any) by the Guarantor shall be made
without withholding or deduction for or on account of any Relevant Tax, unless
the withholding or deduction of such Relevant Tax is required by law. In that
event, the Guarantor shall pay, as further Guarantee Payments, such additional
amounts as may be necessary in order that the net amounts received by a Holder
(or a third party on its behalf) after such withholding or deduction will equal
the amount which would have been received in respect of the Guarantee Payments
(including interest accrued thereon, if any) in the absence of such withholding
or deduction ("Guarantee Additional Amounts"), except that no such Guarantee
Additional Amounts shall be payable to a Holder (or a third party on its behalf)
with respect to any Guarantee Payments (including interest accrued thereon, if
any) (i) to the extent that such Relevant Tax is imposed or levied by virtue of
such Holder (or the beneficial owner of Common Securities to which such
Guarantee Payments relate) having some connection with the Relevant
Jurisdiction, other than being a Holder (or beneficial owner) of Common
Securities ) or (ii) to the extent that such Relevant Tax is imposed or levied
by virtue of such Holder (or beneficial owner) not having made a declaration of
non-residence in, or other lack of connection with, the Relevant Jurisdiction of
any similar claim for exemption, if the Guarantor or its agent has provided the
beneficial owner of such Common Securities or its nominee with at least 60 days'
prior written notice of any opportunity to make such a declaration or claim.

                                  ARTICLE VI.

                    LIMITATION OF TRANSACTIONS; SUBORDINATION

      Section 6.1. Limitation of Transactions. So long as any Preferred
Securities remain outstanding, if there shall have occurred and be continuing an
Event of Default or an event of

                                       13
<PAGE>

default under the Trust Agreement, then (a) the Guarantor shall not declare or
pay any dividend on, make any distributions with respect to, or redeem,
purchase, acquire or make a liquidation payment with respect to, any of its
capital stock (other than (i) purchases or acquisitions of shares of its common
stock in connection with the satisfaction by the Guarantor of its obligations
under any employee benefit plans or the satisfaction by the Guarantor of its
obligations pursuant to any contract or security requiring the Guarantor to
purchase shares of its common stock, (ii) as a result of a reclassification of
its capital stock or the exchange or conversion of one class or series of its
capital stock for another class or series of its capital stock, (iii) the
purchase of fractional interests in shares of its capital stock pursuant to the
conversion or exchange provisions of such capital stock or the security being
converted or exchanged, and (iv) redemptions or purchases pursuant to the
Guarantor's Rights Agreement, dated as of May 11, 1999, as amended, between the
Guarantor and Wells Fargo Bank Minnesota, N.A., as successor in interest to
ChaseMellon Shareholder Services, LLC), (b) the Guarantor shall not make any
payment of interest, principal or premium, if any, on or repay, repurchase or
redeem any debt securities (including guarantees) issued by the Guarantor which
rank pari passu with or junior to the Debentures and (c) the Guarantor shall not
make any guarantee payments with respect to the foregoing (other than pursuant
to this Agreement and the Common Securities Guarantee, dated as of July 26, 2005
of the Guarantor with respect to the 6.750% Trust Originated Common Securities
of the Trust), the Common Securities Guarantee Agreement, dated as of December
20, 1996 and the Capital Securities Guarantee Agreement, dated as of June 6,
1997 (the "Capital Guarantee")).

      Section 6.2. Subordinated Ranking. This Preferred Securities Guarantee
will constitute an unsecured obligation of the Guarantor and will rank (i)
subordinate and junior in right of payment to all Senior Indebtedness (as such
term is defined in the Indenture), (ii) pari passu with the Debentures, the
8.197% Junior Subordinated Deferrable Interest Debentures due May, 2045, the
Guarantor's Capital Guarantee and any other liabilities or obligations that may
be pari passu by their terms and (iii) senior to the Guarantor's common stock,
the Common Securities Guarantee, the Common Securities Guarantee Agreement dated
as of December 20, 1996, the most senior preferred or preference stock now or
hereafter issued by the Guarantor and with any guarantee now or hereafter
entered into by the Guarantor in respect of any preferred or preference stock of
any affiliate of the Guarantor.

                                  ARTICLE VII.

                                   TERMINATION

      Section 7.1. Termination. This Preferred Securities Guarantee shall
terminate upon (i) full payment of the Redemption Price of all Preferred
Securities, (ii) upon the distribution of the Debentures to the Holders of all
of the Preferred Securities or (iii) upon full payment of the amounts payable in
accordance with the Trust Agreement upon liquidation of the Issuer.
Notwithstanding the foregoing, this Preferred Securities Guarantee will continue
to be effective or will be reinstated, as the case may be, if at any time any
Holder of Preferred Securities must restore payment of any sums paid under the
Preferred Securities or under this Preferred Securities Guarantee.

                                       14
<PAGE>

                                 ARTICLE VIII.

                                INDEMNIFICATION

      Section 8.1. Exculpation. (a) No Indemnified Person shall be liable,
responsible or accountable in damages or otherwise to the Guarantor or any
Covered Person for any loss, damage or claim incurred by reason of any act or
omission performed or omitted by such Indemnified Person in good faith in
accordance with this Preferred Securities Guarantee and in a manner that such
Indemnified Person reasonably believed to be within the scope of the authority
conferred on such Indemnified Person by this Preferred Securities Guarantee or
by law, except that an Indemnified Person shall be liable for any such loss,
damage or claim incurred by reason of such Indemnified Person's negligence or
willful misconduct with respect to such acts or omissions.

            (b) An Indemnified Person shall be fully protected in relying in
      good faith upon the records of the Guarantor and upon such information,
      opinions, reports or statements presented to the Guarantor by any Person
      as to matters the Indemnified Person reasonably believes are within such
      other Person's professional or expert competence and who has been selected
      with reasonable care by or on behalf of the Guarantor, including
      information, opinions, reports or statements as to the value and amount of
      the assets, liabilities, profits, losses, or any other facts pertinent to
      the existence and amount of assets from which Distributions to Holders of
      Preferred Securities might properly be paid.

      Section 8.2. Indemnification.

            (a) To the fullest extent permitted by applicable law, the Guarantor
      shall indemnify and hold harmless each Indemnified Person from and against
      any loss, damage or claim incurred by such Indemnified Person by reason of
      any act or omission performed or omitted by such Indemnified Person in
      good faith in accordance with this Guarantee Agreement and in a manner
      such Indemnified Person reasonably believed to be within the scope of
      authority conferred on such Indemnified Person by this Guarantee
      Agreement, except that no Indemnified Person shall be entitled to be
      indemnified in respect of any loss, damage or claim incurred by such
      Indemnified Person by reason of negligence or willful misconduct with
      respect to such acts or omissions.

            (b) To the fullest extent permitted by applicable law, reasonable
      expenses (including legal fees) incurred by an Indemnified Person in
      defending any claim, demand, action, suit or proceeding shall, from time
      to time, be advanced by the Guarantor prior to the final disposition of
      such claim, demand, action, suit or proceeding upon receipt by the
      Guarantor of an undertaking by or on behalf of the Indemnified Person to
      repay such amount if it shall be determined that the Indemnified Person is
      not entitled to be indemnified as authorized in Section 8.2(a).

            (c) The obligation to indemnify as set forth in this Section 8.2
      shall survive the termination of the Preferred Securities Guarantee.

                                       15
<PAGE>

                                  ARTICLE IX.

                                 MISCELLANEOUS

      Section 9.1. Successors and Assigns. All guarantees and agreements
contained in this Preferred Securities Guarantee shall bind the successors,
assigns, receivers, trustees and representatives of the Guarantor and shall
inure to the benefit of the Holders of the Preferred Securities then
outstanding.

      Section 9.2. Amendments. Except with respect to any changes that do not
adversely affect the rights of Holders (in which case no consent of Holders will
be required), this Preferred Securities Guarantee may only be amended with the
prior approval of the Holders of at least a Majority in liquidation amount
(including the stated amount that would be paid on redemption, liquidation or
otherwise, plus accrued and unpaid Distributions to the date upon which the
voting percentages are determined) of all the outstanding Preferred Securities.
The provisions of Section 12.2 of the Trust Agreement with respect to meetings
of Holders of the Securities apply to the giving of such approval.

      Section 9.3. Notices. All notices provided for in this Preferred
Securities Guarantee shall be in writing, duly signed by the party giving such
notice, and shall be delivered, telecopied or mailed by registered or certified
mail, as follows:

            (a) if given to the Preferred Guarantee Trustee, at the Preferred
      Guarantee Trustee's mailing address set forth below (or such other address
      as the Preferred Guarantee Trustee may give notice of to the Holders of
      the Preferred Securities):

                The Bank of New York
                101 Barclay Street, 8W
                New York, New York 10286
                Facsimile: (212) 815-5704
                Attention: Geovanni Barris

            (b) If given to the Guarantor, at the Guarantor's mailing address
      set forth below (or such other address as the Guarantor may give notice of
      to the Holders of the Preferred Securities):

                W. R. Berkley Corporation
                475 Steamboat Road
                Greenwich, Connecticut 06830
                Facsimile No.: (203) 769-4098
                Attention: Ira S. Lederman

            (c) If given to any Holder of Preferred Securities, at the address
      set forth on the books and records of the Issuer.

      All such notices shall be deemed to have been given when received in
person, telecopied with receipt confirmed, or mailed by first class mail,
postage prepaid except that if a notice or other document is refused delivery or
cannot be delivered because of a changed address of which

                                       16
<PAGE>

no notice was given, such notice or other document shall be deemed to have been
delivered on the date of such refusal or inability to deliver.

      Section 9.4. Benefit. This Preferred Securities Guarantee is solely for
the benefit of the Holders of the Preferred Securities and, subject to Section
3.1(a), is not separately transferable from the Preferred Securities.

      Section 9.5. Governing Law. THIS PREFERRED SECURITIES GUARANTEE SHALL BE
GOVERNED BY, AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE
STATE OF NEW YORK.

                                       17
<PAGE>

      THIS PREFERRED SECURITIES GUARANTEE is executed as of the day and year
first above written.

                                        W. R. BERKLEY CORPORATION, as Guarantor

                                        By: /s/ Eugene G. Ballard
                                            ------------------------------------
                                           Name: Eugene G. Ballard
                                           Title: Senior Vice President

                                        THE BANK OF NEW YORK, as Preferred
                                        Guarantee Trustee

                                        By: /s/ Stacey B. Poindexter
                                            ------------------------------------
                                           Name: Stacey B. Poindexter
                                           Title: Assistant Vice President

                                       18

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