<PAGE>


                       FIRST AMENDMENT TO CREDIT AGREEMENT
                       -----------------------------------

     THIS FIRST AMENDMENT TO CREDIT AGREEMENT, dated as of December 8, 2000
(this "Amendment"), amends the Credit Agreement, dated as of December 10, 1999
(the "Credit Agreement"), among W.R. BERKLEY CORPORATION, a Delaware corporation
(the "Company"), the various financial institutions parties thereto
(collectively, the "Banks") and Bank of America National Association, as
administrative agent (the "Agent") for the Banks. Terms defined in the Credit
Agreement are, unless otherwise defined herein or the context otherwise
requires, used herein as defined therein.

     WHEREAS, the parties hereto have entered into the Credit Agreement, which
provides for the Banks to extend certain credit facilities to the Borrower from
time to time; and

     WHEREAS, the parties hereto desire to amend the Credit Agreement in certain
respects as hereinafter set forth;

     NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration (the receipt and sufficiency of which are hereby
acknowledged), the parties hereto agree as follows:

     SECTION 1 AMENDMENTS. Effective as of December 8, 2000, the Credit
Agreement shall be amended in accordance with Sections 1.1 through 1.12 below.

     1.1 Applicable Margin. The definition of "Applicable Facility Fee Rate,"
"Applicable Margin" and "Applicable Utilization Fee Rate" shall be amended to
state in its entirety as follows:

     "Applicable Facility Fee Rate", "Applicable Margin" and "Applicable
Utilization Fee Rate" means the following percentages (expressed in basis
points) from time to time based upon the then applicable senior unsecured,
unsupported debt rating of the Company assigned by S&P and Moody's:

<TABLE>
<CAPTION>
                                                Level I         Level II          Level III       Level IV
                                                -------         --------          ---------       --------
<S>                                             <C>             <C>               <C>             <C>
                                                                BBB+/Baa1
Senior Unsecured Debt Rating                    A-/A3           or BBB/Baa2       BBB-/Baa3       BB+/Ba1

Applicable Facility Fee Rate                    12.50 bps       22.50 bps         32.50 bps       40.00 bps

Applicable Margin for Offshore Rate Loans       62.50 bps       77.50 bps         82.50 bps       100.00 bps

Application Margin for Base Rate Loans          0 bps           0 bps             0 bps           0 bps

Applicable Utilization Fee Rate                 0 bps           0 bps             10.0 bps        10.0 bps
</TABLE>

     The Applicable Facility Fee Rate, Applicable Margin and Applicable
Utilization Fee Rate shall be determined based upon the higher of the Company's
senior debt rating from S&P or Moody's except that if the Company's senior debt
rating differs by more than one level between such ratings from S&P and Moody's,
the Applicable Facility Fee Rate, Applicable Margin and Applicable Utilization
Fee Rate shall be one level higher than the lower such rating. In the event the
Company's senior debt is unrated by both S&P and Moody's, the Applicable
Facility Fee



<PAGE>


Rate, the Applicable Margin and the Applicable Utilization Fee Rate shall be
determined as if Level IV were applicable until the senior debt shall be rated.

     1.2 Debt Ratio. The definition of "Debt Ratio" in Section 1.1 of the Credit
Agreement is hereby amended to state in its entirety as follows:

          "Debt Ratio" shall mean the ratio of (i) all Indebtedness of the
     Company and its Subsidiaries on a consolidated basis (other than
     obligations under Swap Contracts consisting only of options with respect to
     equity investments held in a merger arbitrage portfolio of the Company or
     any Subsidiary which obligations were entered into for the purpose of
     hedging risk with respect to such portfolio) to (ii) Total Capital.

     1.3 Revolving Termination Date. The definition of "Revolving Termination
Date" in Section 1.1 of the Credit Agreement is hereby amended by the deletion
of the date "December 8, 2000" and the substitution therefor of the date
"December 7, 2001."

     1.4 Total Capital. The definition of "Total Capital" in Section 1.1 of the
Credit Agreement is hereby amended to state in its entirety as follows:

          "Total Capital" means Stockholder's Equity plus Indebtedness of the
     Company and its Subsidiaries on a consolidated basis plus the non
     duplicative principal amount of Deferrable Interest Debentures.

     1.5 Certificate. The references in Section 4.1(f) of the Credit Agreement
to "December 31, 1998" shall be amended to be references to "December 31, 1999."

     1.6 Financial Condition. The references in Section 5.11 of the Credit
Agreement to "December 31, 1998" and "September 30, 1999" shall be amended to be
references to "December 31, 1999" and "September 30, 2000," respectively.

     1.7 Minimum Common Stockholder's Equity. Section 7.9(a) of the Credit
Agreement is hereby amended to state in its entirety as follows:

          "(a) Minimum Common Stockholder's Equity. The Company shall not at any
     time permit Common Stockholder's Equity to be less than $625,000,000 plus
     25% of net income (if positive) determined on a cumulative basis for the
     period after December 31, 2000."

     1.8 Debt Ratio. Section 7.9(b) of the Credit Agreement is hereby amended by
the deletion of the ratio "0.40:1" and the substitution therefor of the ratio
"0.35:1."

     1.9 Schedule 2.1. Schedule 2.1 of the Credit Agreement is hereby amended to
state in its entirety as set forth in Schedule 2.1 hereto.

     1.10 Schedule 5.7. Schedule 5.7 of the Credit Agreement is hereby amended
to state in its entirety as set forth in Schedule 5.7 hereto.


                                      -2-

<PAGE>


     1.11 Schedule 5.16. The reference in Section 5.16 of the Credit Agreement
to "December 31, 1998" shall be amended to be a reference to "December 31,
1999." Schedule 5.16 of the Credit Agreement is hereby amended to state in its
entirety as set forth in Schedule 5.16 hereto.

     1.12 Exiting Bank. As of the date hereof, Wells Fargo Bank, N.A. (the
"Exiting Bank") shall no longer be a "Bank" under this Agreement. The Company
shall on the date hereof repay the principal of all outstanding Loans made by
the Exiting Bank, together with accrued interest, fees and other amounts payable
to the Exiting Bank. BofA shall make a Loan on the date hereof to the Company in
an amount equal to the Loan repaid to the Exiting Bank with an Interest Period
ending on the last day of the Interest Period applicable to the repaid Loan and
with an interest rate equal to the rate applicable to the repaid Loan. If BofA
shall incur any cost or expense as a result of funding said Loan after the
commencement of the applicable Interest Period, the Company shall reimburse BofA
for such cost or expense.

     SECTION 2 CONDITIONS PRECEDENT. This Amendment shall become effective when
each of the conditions precedent set forth in this Section 2 shall have been
satisfied, and notice thereof shall have been given by the Agent to the Company
and the Banks.

     2.1 Receipt of Documents. The Agent shall have received all of the
following documents duly executed, dated the date hereof or such other date as
shall be acceptable to the Agent, and in form and substance satisfactory to the
Agent:

          (a) Amendment. This Amendment, duly executed by the Company, the Agent
     and the Banks.

          (b) Secretary's Certificate. A certificate of the secretary or an
     assistant secretary of the Company, as to (i) resolutions of the Board of
     Directors of the Company then in full force and effect authorizing the
     execution, delivery and performance of this Amendment and each other
     document described herein, and (ii) the incumbency and signatures of those
     officers of the Company authorized to act with respect to this Amendment
     and each other document described herein.

          (c) Opinion of Counsel. An opinion, addressed to the Agent and all
     Banks, from Willkie, Farr & Gallagher, counsel to the Company.

     2.2 Compliance with Warranties, No Default, etc. Both before and after
giving effect to the effectiveness of this Amendment, the following statements
by the Company shall be true and correct (and the Company, by its execution of
this Amendment, hereby represents and warrants to the Agent and each Bank that
such statements are true and correct as at such times):

          (a) the representations and warranties set forth in Article V of the
     Credit Agreement shall be true and correct with the same effect as if then
     made (unless stated to relate solely to an earlier date, in which case such
     representations and warranties shall be true and correct as of such earlier
     date); and

          (b) no Event of Default or Default shall have then occurred and be
     continuing.


                                      -3-

<PAGE>


     2.3 Payment of Fees. The Company shall have paid to the Agent and the Banks
all fees then due and payable to the extent then invoiced.

     SECTION 3 REPRESENTATIONS AND WARRANTIES. To induce the Banks and the Agent
to enter into this Amendment, the Company hereby reaffirms, as of the date
hereof (unless stated to relate solely to an earlier date, in which case such
representations and warranties shall be true and correct as of such earlier
date), its representations and warranties contained in Article V of the Credit
Agreement and the Company additionally represents and warrants to the Agent and
each Bank as follows:

     3.1 Due Authorization, Non-Contravention, etc. The execution, delivery and
performance by the Company of this Amendment are within the Company's corporate
powers, have been duly authorized by all necessary corporate action, and do not

          (a) contravene the Company's Organization Documents;

          (b) contravene any contractual restriction, law or governmental
     regulation or court decree or order binding on or affecting the Company; or

          (c) result in, or require the creation or imposition of, any Lien on
     any of the Company's properties.

     3.2 Government Approval, Regulation, etc. No authorization or approval or
other action by, and no notice to or filing with, any governmental authority or
regulatory body or other Person is required for the due execution, delivery or
performance by the Company of this Amendment.

     3.3 Validity, etc. This Amendment constitutes the legal, valid and binding
obligation of the Company enforceable in accordance with its terms

SECTION 4 MISCELLANEOUS.

     4.1 Continuing Effectiveness, etc. This Amendment shall be deemed to be an
amendment to the Credit Agreement, and the Credit Agreement, as amended hereby,
shall remain in full force and effect and is hereby ratified, approved and
confirmed in each and every respect. After the effectiveness of this Amendment
in accordance with its terms, all references to the Credit Agreement in the Loan
Documents or in any other document, instrument, agreement or writing shall be
deemed to refer to the Credit Agreement as amended hereby.

     4.2 Payment of Costs and Expenses. The Company agrees to pay on demand all
expenses of the Agent (including the reasonable fees and out-of-pocket expenses
of counsel to the Agent) in connection with the negotiation, preparation,
execution and delivery of this Amendment.

     4.3 Severability. Any provision of this Amendment which is prohibited or
unenforceable in any jurisdiction shall, as to such provision and such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions


                                      -4-

<PAGE>


of this Amendment or affecting the validity or enforceability of such provision
in any other jurisdiction.

     4.4 Headings. The various headings of this Amendment are inserted for
convenience only and shall not affect the meaning or interpretation of this
Amendment or any provisions hereof.

     4.5 Execution in Counterparts. This Amendment may be executed by the
parties hereto in several counterparts, each of which shall be deemed to be an
original and all of which shall constitute together but one and the same
agreement.

     4.6 Governing Law. THIS AMENDMENT SHALL BE DEEMED TO BE A CONTRACT MADE
UNDER AND GOVERNED BY THE INTERNAL LAWS OF THE STATE OF ILLINOIS.

     4.7 Successors and Assigns. This Amendment shall be binding upon and shall
inure to the benefit of the parties hereto and their respective successors and
assigns.


                                      -5-

<PAGE>


     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their respective officers thereunto duly authorized as of the day
and year first above written.

                                        W. R. BERKLEY CORPORATION


                                        By: /s/ Eugene Ballard
                                            ------------------------------
                                            Title: Senior Vice President

                                        BANK OF AMERICA, N.A.


                                        By: /s/ Elizabeth W.F. Bishop
                                            ------------------------------
                                            Title: Principal


<PAGE>


                                  SCHEDULE 2.1
                                  ------------

                                   COMMITMENTS
                                   -----------
                               AND PRO RATA SHARES
                               -------------------

                                                                        Pro Rata
       Bank                              Commitment                       Share
       ----                              ----------                       -----
Bank of America,                         $50,000,000                      100%
National Association

         TOTAL                           $50,000,000                      100%