<PAGE>

                                                                     Exhibit 4.1



                               MARKEL CORPORATION
                                     Issuer

                                       TO

                               JPMORGAN CHASE BANK
                  (formerly known as The Chase Manhattan Bank)
                                     Trustee


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


                          Second Supplemental Indenture

                          Dated as of February 25, 2003


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


                                  $200,000,000

                                6.8% Senior Notes

                                    Due 2013




<PAGE>

                               TABLE OF CONTENTS*

ARTICLE I 6.8% SENIOR NOTES DUE 2013                                      1
  SECTION 101.     ESTABLISHMENT                                          1
  SECTION 102.     DEFINITIONS                                            2
  SECTION 103.     PAYMENT OF PRINCIPAL AND INTEREST                      3
  SECTION 104.     DENOMINATIONS                                          4
  SECTION 105.     GLOBAL SECURITIES                                      4
  SECTION 106.     REDEMPTION                                             5
  SECTION 107.     SINKING FUND                                           5
  SECTION 108.     ADDITIONAL INTEREST                                    5
  SECTION 109.     PAYING AGENT                                           5
  SECTION 110.     LIMITATION ON LIENS                                    5
  SECTION 111.     EVENTS OF DEFAULT                                      6
  SECTION 112.     DEFEASANCE                                             8

ARTICLE II MISCELLANEOUS PROVISIONS                                       8

  SECTION 201.     RECITALS BY COMPANY                                    8
  SECTION 202.     RATIFICATION AND INCORPORATION OF ORIGINAL INDENTURE   8
  SECTION 203.     EXECUTED IN COUNTERPARTS                               8
  SECTION 204.     ASSIGNMENT                                             9

* This Table of Contents does not constitute part of the Indenture or have any
bearing upon the interpretation of any of its terms and provisions.


                                       i



<PAGE>

         THIS SECOND SUPPLEMENTAL INDENTURE is made as of February 25, 2003, by
and between MARKEL CORPORATION, a Virginia corporation, having its principal
office at 4521 Highwoods Parkway, Glen Allen, Virginia 23060 (the "Company"),
and JPMORGAN CHASE BANK (formerly known as THE CHASE MANHATTAN BANK), a New York
banking corporation, as Trustee (herein called the "Trustee").

                              W I T N E S S E T H:

         WHEREAS, the Company has heretofore entered into a Senior Indenture,
dated as of June 5, 2001 (the "Original Indenture"), as heretofore supplemented
and amended, with the Trustee;

         WHEREAS, the Original Indenture is incorporated herein by this
reference and the Original Indenture, as heretofore supplemented and amended and
as further supplemented by this Second Supplemental Indenture, is herein called
the "Indenture";

         WHEREAS, under the Original Indenture, a new series of Securities may
at any time be established in accordance with the provisions of the Original
Indenture and the terms of such series may be described by a supplemental
indenture executed by the Company and the Trustee;

         WHEREAS, the Company proposes to create under the Indenture a series of
Securities;

         WHEREAS, additional Securities of other series hereafter established,
except as may be limited in the Original Indenture as at the time supplemented
and modified, may be issued from time to time pursuant to the Indenture as at
the time supplemented and modified; and

         WHEREAS, all conditions necessary to authorize the execution and
delivery of this Second Supplemental Indenture and to make it a valid and
binding obligation of the Company have been done or performed.

         NOW, THEREFORE, in consideration of the agreements and obligations set
forth herein and for other good and valuable consideration, the sufficiency of
which is hereby acknowledged, the parties hereto hereby agree as follows:

                                   ARTICLE I
                           6.8% SENIOR NOTES due 2013

         Section 101. Establishment. There is hereby established a new series of
Securities to be issued under the Indenture, to be designated as the Company's
6.8% Senior Notes Due 2013 (the "6.8% Senior Notes").

         There are to be authenticated and delivered $200,000,000 principal
amount of 6.8% Senior Notes, and such principal amount of the 6.8% Senior Notes
may be increased from time to time pursuant to Section 301 of the Indenture. All
6.8% Senior Notes need not be issued at the same time and such series may be
reopened at any time, without the consent of any Holder, for issuances of
additional 6.8% Senior Notes. Any such additional 6.8% Senior Notes will have
the same interest rate, maturity and other terms as those initially issued.
Further 6.8% Senior



<PAGE>

Notes may also be authenticated and delivered as provided by Sections 304, 305,
306 or 905 of the Original Indenture.

         The 6.8% Senior Notes shall be issued in definitive fully registered
form without coupons, in substantially the form set out in Exhibit A hereto. The
entire initially issued principal amount of the 6.8% Senior Notes shall
initially be evidenced by one or more certificates issued to Cede & Co., as
nominee for The Depository Trust Company.

         The form of the Trustee's Certificate of Authentication for the 6.8%
Senior Notes shall be in substantially the form set forth in Exhibit B hereto.

         Each 6.8% Senior Note shall be dated the date of authentication thereof
and shall bear interest from the Original Issue Date or from the most recent
Interest Payment Date to which interest has been paid or duly provided for.

Section 102. Definitions. The following defined terms used herein shall, unless
the context otherwise requires, have the meanings specified below. Capitalized
terms used herein for which no definition is provided herein shall have the
meanings set forth in the Original Indenture.

         "Business Day" means a day other than (i) a Saturday or a Sunday, (ii)
a day on which banks in New York, New York are authorized or obligated by law or
executive order to remain closed or (iii) a day on which the Corporate Trust
Office is closed for business.

         "Corporate Trust Office" means the office of the Trustee at which at
any particular time its corporate trust business shall be principally
administered, which office at the date of original execution of this Indenture
is located at 4 New York Plaza, 15th Floor, New York, New York 10004.

         "Interest Payment Dates" means February 15 and August 15 of each year,
commencing on August 15, 2003.

         "Lien" means any mortgage, lien, pledge, security interest or other
encumbrance of any kind.

         "Material Subsidiary" means a Subsidiary of the Company whose total
assets (as determined in accordance with GAAP) represent at least 20% of the
total assets of the Company on a consolidated basis.

         "Original Issue Date" means February 25, 2003.

         "Outstanding", when used with respect to the 6.8% Senior Notes, means,
as of the date of determination, all 6.8% Senior Notes, theretofore
authenticated and delivered under the Indenture, except:

         (i) 6.8% Senior Notes theretofore canceled by the Trustee or delivered
to the Trustee for cancellation;

                                       2




<PAGE>

     (ii) 6.8% Senior Notes for whose payment at Maturity the necessary amount
of money or money's worth has been theretofore deposited (other than pursuant to
Section 402 of the Original Indenture) with the Trustee or any Paying Agent
(other than the Company) in trust or set aside and segregated in trust by the
Company (if the Company shall act as its own Paying Agent) for the Holders of
such 6.8% Senior Notes.

     (iii) 6.8% Senior Notes with respect to which the Company has effected
defeasance, or covenant defeasance has been effected, pursuant to Section 402 of
the Original Indenture; and

     (iv) 6.8% Senior Notes that have been paid pursuant to Section 306 of the
Original Indenture or in exchange for or in lieu of which other 6.8% Senior
Notes have been authenticated and delivered pursuant to the Indenture, other
than any such 6.8% Senior Notes in respect of which there shall have been
presented to the Trustee proof satisfactory to it that such 6.8% Senior Notes
are held by a bona fide purchaser in whose hands such 6.8% Senior Notes are
valid obligations of the Company; provided, however, that in determining whether
the Holders of the requisite principal amount of Outstanding 6.8% Senior Notes
have given any request, demand, authorization, direction, notice, consent or
waiver hereunder or are present at a meeting of Holders of 6.8% Senior Notes for
quorum purposes, 6.8% Senior Notes owned by the Company or any other obligor
upon the 6.8% Senior Notes or any Affiliate of the Company or such other obligor
shall be disregarded and deemed not to be Outstanding, except that, in
determining whether the Trustee shall be protected in making any such
determination or relying upon any such request, demand, authorization,
direction, notice, consent or waiver, only 6.8% Senior Notes which a Responsible
Officer of the Trustee knows to be so owned shall be so disregarded. 6.8% Senior
Notes so owned which shall have been pledged in good faith may be regarded as
Outstanding if the pledgee establishes to the satisfaction of the Trustee (A)
the pledgee's right so to act with respect to such 6.8% Senior Notes and (B)
that the pledgee is not the Company or any other obligor upon the 6.8% Senior
Notes or an Affiliate of the Company or such other obligor.

     "Regular Record Date" means, with respect to each Interest Payment
Date, the close of business on the Business Day preceding such Interest Payment
Date; provided, that with respect to 6.8% Senior Notes that are not represented
by one or more Global Securities, the Regular Record Date shall be the close of
business on the 15th calendar day (whether or not a Business Day) preceding such
Interest Payment Date.

     "Stated Maturity" means February 15, 2013.

     Section 103. Payment of Principal and Interest. The principal of the 6.8%
Senior Notes shall be due at the Stated Maturity. The unpaid principal amount of
the 6.8% Senior Notes shall bear interest at the rate of 6.8% per annum until
paid or duly provided for, such interest to accrue from the Original Issue Date
or from the most recent Interest Payment Date to which interest has been paid or
duly provided for. Interest shall be paid semi-annually in arrears on each
Interest Payment Date to the Person in whose name the 6.8% Senior Notes are
registered on the Regular Record Date for such Interest Payment Date; provided
that interest payable at the Stated Maturity of principal as provided herein
will be paid to the Person to whom principal is payable. Any such interest that
is not so punctually paid or duly provided for will forthwith cease to be
payable to the Holders on such Regular Record Date and may either be

                                       3


<PAGE>

paid to the Person or Persons in whose name the 6.8% Senior Notes are registered
at the close of business on a Special Record Date for the payment of such
defaulted interest to be fixed by the Trustee (in accordance with Section 307 of
the Original Indenture), notice whereof shall be given to Holders of the 6.8%
Senior Notes not less than ten (10) days prior to such Special Record Date, or
be paid at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange, if any, on which the 6.8% Senior Notes
may be listed, and upon such notice as may be required by any such exchange, all
as more fully provided in the Original Indenture.

         Payments of interest on the 6.8% Senior Notes will include interest
accrued to but excluding the respective Interest Payment Dates. Interest
payments for the 6.8% Senior Notes shall be computed and paid on the basis of a
360-day year of twelve 30-day months. In the event that any date on which
interest is payable on the 6.8% Senior Notes is not a Business Day, then payment
of the interest payable on such date will be made on the next succeeding day
that is a Business Day (and without any interest or payment in respect of any
such delay), in each case with the same force and effect as if made on the date
the payment was originally payable.

         Payment of the principal and interest on the 6.8% Senior Notes shall be
made at the office of the Paying Agent 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, with any such payment that is due at the Stated
Maturity of any 6.8% Senior Notes being made upon surrender of such 6.8% Senior
Notes to the Paying Agent. Payments of interest (including interest on any
Interest Payment Date) will be made, subject to such surrender where applicable,
at the option of the Company, (i) by check mailed to the address of the Person
entitled thereto as such address shall appear in the Security Register or (ii)
by wire transfer at such place and to such account at a banking institution in
the United States as may be designated in writing to the Trustee at least
sixteen (16) days prior to the date for payment by the Person entitled thereto.
In the event that any date on which principal and interest is payable on the
6.8% Senior Notes is not a Business Day, then payment of the principal and
interest payable on such date will be made on the next succeeding day that is a
Business Day (and without any interest or payment in respect of any such delay),
in each case with the same force and effect as if made on the date the payment
was originally payable.

     Section 104. Denominations. The 6.8% Senior Notes may be issued in
denominations of $1,000, or any integral multiple thereof.


     Section 105. Global Securities. The 6.8% Senior Notes will be issued
initially in the form of one or more Global Securities registered in the name of
the Depositary (which shall be The Depository Trust Company) or its nominee.
Except under the limited circumstances described below, 6.8% Senior Notes
represented by such Global Securities will not be exchangeable for, and will not
otherwise be issuable as, 6.8% Senior Notes in definitive form. The Global
Securities described above may not be transferred except 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 or to a successor Depositary or its nominee.

                                       4




<PAGE>

     Owners of beneficial interests in such a Global Security will not be
considered the Holders thereof for any purpose under the Indenture, and no
Global Security representing a 6.8% Senior Note shall be exchangeable, except
for another Global Security of like denomination and tenor to be registered in
the name of the Depositary or its nominee or to a successor Depositary or its
nominee or except as described below. The rights of Holders of such Global
Security shall be exercised only through the Depositary.

     A Global Security shall be exchangeable for 6.8% Senior Notes
registered in the names of persons other than the Depositary or its nominee only
if (i) the Depositary notifies the Company that it is unwilling or unable to
continue as a Depositary for such Global Security and no successor Depositary
shall have been appointed by the Company within 90 days of receipt by the
Company of such notification, or if at any time the Depositary ceases to be a
clearing agency registered under the Exchange Act at a time when the Depositary
is required to be so registered to act as such Depositary and no successor
Depositary shall have been appointed by the Company within 90 days after it
becomes aware of such cessation, or (ii) the Company in its sole discretion
determines that such Global Security shall be so exchangeable. Any Global
Security that is exchangeable pursuant to the preceding sentence shall be
exchangeable for 6.8% Senior Notes registered in such names as the Depositary
shall direct.

     Section 106. Redemption. The 6.8% Senior Notes are not redeemable, in whole
or in part, at any time.


     Section 107. Sinking Fund. The 6.8% Senior Notes shall not have a sinking
fund.


     Section 108. Additional Interest. Any principal of and installment of
interest on the 6.8% Senior Notes that is overdue shall bear interest at the
rate of 6.8% (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.

     Section 109. Paying Agent. The Trustee shall initially serve as Paying
Agent with respect to the 6.8% Senior Notes, with the Place of Payment initially
being the Corporate Trust Office of the Trustee.

     Section 110. Limitation on Liens. The Company and its Material Subsidiaries
may not issue, assume, incur or guarantee any indebtedness for borrowed money
secured by a mortgage, pledge, lien or other encumbrance, directly or
indirectly, upon any shares of the Voting Stock of a Material Subsidiary which
shares are owned by the Company or its Material Subsidiaries without effectively
providing that the 6.8% Senior Notes (and if the Company so elects, any other
indebtedness of the Company ranking on a parity with the 6.8% Senior Notes)
shall be secured equally and ratably with, or prior to, any such secured
indebtedness so long as such indebtedness remains outstanding. This Section 110
shall not apply to:

     (i) liens for taxes or assessments or governmental charges or levies
not then due and delinquent or the validity of which is being contested in good
faith or which are less than $1,000,000 in amount and liens created by or
resulting from any litigation or legal proceeding

                                       5


<PAGE>

which is currently being contested in good faith by appropriate proceedings or
which involves claims of less than $1,000,000, or

         (ii) any mortgage, pledge, lien or other encumbrance upon any shares of
Voting Stock of any corporation existing at the time such corporation becomes a
Material Subsidiary and any extensions, renewals or replacements thereof.

         This Section 110 has been included in this Second Supplemental
Indenture expressly and solely for the benefit of the 6.8% Senior Notes and
shall be subject to covenant defeasance pursuant to Section 402(3) of the
Original Indenture.

          Section 111. Events of Default. Article V of the Original Indenture is
amended solely with respect to the 6.8% Senior Notes as follows:

         (a) Section 501 is amended and restated in its entirety as follows:

         "Section 501.  Events of Default.

                  `Event of Default', wherever used herein with respect to the
         6.8% Senior Notes, means any one of the following events (whatever the
         reason for such Event of Default and whether it shall be voluntary or
         involuntary or be effected by operation of law or pursuant to any
         judgment, decree or order of any court or any order, rule or regulation
         of any administrative or governmental body):

                  (1) default in the payment of any interest on the 6.8% Senior
         Notes when such interest becomes due and payable, and continuance of
         such default for a period of 30 days; or

                  (2) default in the payment of the principal of the 6.8% Senior
         Notes when due upon Maturity; or

                  (3) default in the performance, or breach, of any covenant or
         warranty of the Company in this Indenture or the Security representing
         the 6.8% Senior Notes (other than (i) a covenant or warranty for which
         the consequences of breach or nonperformance are addressed elsewhere in
         this Section 501 or (ii) a covenant or warranty which has expressly
         been included in this Indenture or a Security of a series, whether or
         not by means of a supplemental indenture, solely for the benefit of
         Securities of a series other than the 6.8% Senior Notes), and
         continuance of such default or breach for a period of 60 days after
         there has been given, by registered or certified mail, to the Company
         by the Trustee or to the Company and the Trustee by the Holders of at
         least 25% in principal amount of the Outstanding 6.8% Senior Notes a
         written notice specifying such default or breach and requiring it to be
         remedied and stating that such notice is a `Notice of Default'
         hereunder; or

                  (4) (a) the failure of the Company to make any payment by the
         end of any applicable grace period after maturity of indebtedness,
         which term as used in this Section 501 means obligations (other than
         nonrecourse obligations) of the Company for borrowed

                                       6


<PAGE>

                  money or evidenced by bonds, debentures, notes or similar
         instruments in an aggregate principal amount in excess of $50,000,000
         (`Indebtedness') and continuance of such failure, or (b) the
         acceleration of Indebtedness because of a default with respect to such
         Indebtedness without such Indebtedness having been discharged or such
         acceleration having been cured, waived, rescinded or annulled, in each
         case, for a period of 10 days after written notice to the Company by
         the Trustee or to the Company and the Trustee by the Holders of not
         less than 25% in aggregate principal amount of the Outstanding 6.8%
         Senior Notes; however, if any such failure or acceleration referred to
         in (a) or (b) above ceases or is cured, waived, rescinded or annulled,
         then the Event of Default by reason thereof shall be deemed not to have
         occurred; or

               (5) the Company pursuant to or under or within the meaning of any
          Bankruptcy Law:

                          (a) commences a voluntary case or proceeding;

                          (b) consents to the entry of an order for relief
                  against it in an involuntary case or proceeding or the
                  commencement of any case against it;

                          (c) consents to the appointment of a Custodian of it
                  or for any substantial part of its property;

                          (d) makes a general assignment for the benefit of its
                  creditors;

                          (e) files a petition in bankruptcy or answer or
                  consent seeking reorganization or relief; or

                          (f) consents to the filing of such petition or the
                  appointment of or taking possession by a Custodian; or

               (6) a court of competent jurisdiction enters an order or decree
          under any Bankruptcy Law that:

                          (a) is for relief against the Company in an
                   involuntary case or proceeding, or adjudicates the Company
                   insolvent or bankrupt;

                          (b) appoints a Custodian of the Company or for any
                   substantial part of its property; or

                          (c) orders the winding up or liquidation of the
                   Company;

                   and the order or decree remains unstayed and in effect for 90
days.

               `Bankruptcy Law' means Title 11, United States Code, or any
          similar Federal or state law for the relief of debtors. "Custodian"
          means any receiver, trustee, assignee, liquidator, custodian or
          similar official under any Bankruptcy Law."

                                       7




<PAGE>

         (b) Section 502 is amended as follows:

                  (1) The first paragraph shall be amended by deleting "33%" and
         replacing it with "25%" and by adding the following sentence at the end
         of the paragraph: "If an Event of Default specified in clauses (5) or
         (6) of Section 501 occurs and is continuing, then the principal of, and
         accrued interest on, all of the Outstanding 6.8% Senior Notes shall
         become and be immediately due and payable without any declaration or
         other act on the part of the Trustee or any Holder."

                  (2) The second paragraph shall be amended by deleting the
         period at the end and replacing it with "; and" and by adding the
         following clause immediately after clause (2): "(3) the rescission
         would not conflict with any judgment or decree of a court of competent
         jurisdiction."

     Section 112. Defeasance. In addition to the conditions set forth in Section
402 of the Original Indenture, in order for the Company to effect defeasance or
covenant defeasance of the 6.8% Senior Notes, the Company must have delivered to
the Trustee an Opinion of Counsel to the effect that the Holders of the then
Outstanding 6.8% Senior Notes will not recognize income, gain or loss for
federal income tax purposes as a result of the defeasance or covenant defeasance
and will be subject to federal income tax in the same amounts, in the same
manner and at the same time as would have been the case if the defeasance or
covenant defeasance had not occurred. In the case of a defeasance (but not of a
covenant defeasance), the opinion must refer to and be based upon a ruling of
the Internal Revenue Service or a change in applicable federal income tax laws.

                                   ARTICLE II
                            MISCELLANEOUS PROVISIONS

     Section 201. Recitals by Company. The recitals in this Second Supplemental
Indenture are made by the Company only and not by the Trustee (who makes no
representation for or in respect of the validity or sufficiency of this Second
Supplemental Indenture or for or in respect of the recitals contained herein),
and all of the provisions contained in the Original Indenture in respect of the
rights, privileges, immunities, powers and duties of the Trustee shall be
applicable in respect of the 6.8% Senior Notes and of this Second Supplemental
Indenture as fully and with like effect as if set forth herein in full.

     Section 202. Ratification and Incorporation of Original Indenture. As
supplemented hereby, the Original Indenture is in all respects ratified and
confirmed, and the Original Indenture and this Second Supplemental Indenture
shall be read, taken and construed as one and the same instrument.

     Section 203. Executed in Counterparts. This Second Supplemental Indenture
may be executed in several counterparts, each of which shall be deemed to be an
original, and such counterparts shall together constitute but one and the same
instrument.

                                       8




<PAGE>

     Section 204. Assignment. The Company shall have the right at all times to
assign any of its rights or obligations under the Indenture with respect to the
6.8% Senior Notes to a direct or indirect wholly-owned subsidiary of the
Company; provided that, in the event of any such assignment, the Company shall
remain primarily liable for the performance of all such obligations. The
Indenture may also be assigned by the Company in connection with a transaction
described in Article Eight of the Original Indenture.

IN WITNESS WHEREOF, each party hereto has caused this instrument to be signed in
its name and behalf by its duly authorized officer, all as of the day and year
first above written.

                               MARKEL CORPORATION

                               By:
                                    ---------------------------------------
                               Name:
                                      -------------------------------------
                               Title:
                                       ------------------------------------


                               JPMORGAN CHASE BANK, as Trustee

                               By:
                                    ---------------------------------------
                               Name:
                                      -------------------------------------
                               Title:
                                     --------------------------------------


                                       9



<PAGE>

                                    EXHIBIT A

                                     FORM OF
                            6.8% SENIOR NOTE DUE 2013

         [UNLESS THIS CERTIFICATE 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
CERTIFICATE 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 IS MADE TO [CEDE & CO.], ANY TRANSFER, PLEDGE OR OTHER USE HEREOF
FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE REGISTERED
OWNER HEREOF, [CEDE & CO.], HAS AN INTEREST HEREIN.]**

         [THIS 6.8% SENIOR NOTE IS A GLOBAL SECURITY WITHIN THE MEANING OF THE
INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY
OR A NOMINEE THEREOF. THIS 6.8% SENIOR NOTE MAY NOT BE EXCHANGED IN WHOLE OR IN
PART FOR A SECURITY REGISTERED, AND NO TRANSFER OF THIS 6.8% SENIOR NOTE IN
WHOLE OR IN PART MAY BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH
DEPOSITARY OR A NOMINEE THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED
IN THE INDENTURE.]**

               --------------------------------------------------
                               MARKEL CORPORATION
               --------------------------------------------------
                                  $200,000,000
                           6.8% SENIOR NOTES DUE 2013

No.  A-_                                                     CUSIP No.  _______

         Markel Corporation, a corporation duly organized and existing under the
laws of Virginia (herein called the "Company", which term includes any successor
Person under the Indenture hereinafter referred to), for value received, hereby
promises to pay to [Cede & Co.], or registered assigns (the "Holder"), the
principal sum of Two Hundred Million Dollars ($200,000,000) on February 15, 2013
and to pay interest thereon from February 25, 2003 or from the most recent
Interest Payment Date to which interest has been paid or duly provided for,
semi-annually in


--------
** Insert in Global Securities.

                                       1


<PAGE>

arrears on February 15 and August 15 of each year, commencing on August 15,
2003, at the rate of 6.8% per annum, until the principal hereof is paid or made
available for payment, provided that any principal, and any such installment of
interest, that is overdue shall bear interest at the rate of 6.8% 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. The interest so payable,
and punctually paid or duly provided for, on any Interest Payment Date will, as
provided in such Indenture, be paid to the Person in whose name this 6.8% Senior
Note (or one or more Predecessor Securities) is registered at the close of
business on the Regular Record Date for such interest, which shall be the close
of business on the Business Day preceding such Interest Payment Date; provided,
that with respect to 6.8% Senior Notes that are not represented by one or more
Global Securities, the Regular Record Date shall be the close of business on the
15th calendar day (whether or not a Business Day) preceding such Interest
Payment Date. Any such interest not so punctually paid or duly provided for will
forthwith cease to be payable to the Holder on such Regular Record Date and may
either be paid to the Person in whose name this 6.8% Senior Note (or one or more
Predecessor Securities) is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee, notice whereof shall be given to Holders of 6.8% Senior Notes not less
than 10 days prior to such Special Record Date, or be paid at any time in any
other lawful manner not inconsistent with the requirements of any securities
exchange on which the 6.8% Senior Notes may be listed, and upon such notice as
may be required by such exchange, all as more fully provided in said Indenture.

         Payments of interest on the 6.8% Senior Notes will include interest
accrued to but excluding the respective Interest Payment Dates. Interest
payments for the 6.8% Senior Notes shall be computed and paid on the basis of a
360-day year of twelve 30-day months. In the event that any date on which
interest is payable on the 6.8% Senior Notes is not a Business Day, then payment
of the interest payable on such date will be made on the next succeeding day
that is a Business Day (and without any interest or payment in respect of any
such delay), in each case with the same force and effect as if made on the date
the payment was originally payable.

         Payment of the principal of and interest on this 6.8% Senior Note will
be made at the office of the Paying Agent, in the Borough of Manhattan, City and
State of New York, 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,
with any such payment that is due at the Stated Maturity of any 6.8% Senior Note
being made upon surrender of such 6.8% Senior Note to such office or agency;
provided, however, that at the option of the Company payment of interest,
subject to such surrender where applicable, may be made (i) by check mailed to
the address of the Person entitled thereto as such address shall appear in the
Security Register or (ii) by wire transfer at such place and to such account at
a banking institution in the United States as may be designated in writing to
the Trustee at least sixteen (16) days prior to the date for payment by the
Person entitled thereto.

         Reference is hereby made to the further provisions of this 6.8% Senior
Note set forth on the reverse hereof, which further provisions shall for all
purposes have the same effect as if set forth at this place.

                                       2




<PAGE>

         Unless the certificate of authentication hereon has been executed by
the Trustee referred to on the reverse hereof by manual signature, this 6.8%
Senior Note shall not be entitled to any benefit under the Indenture or be valid
or obligatory for any purpose.

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

Dated:                               Markel Corporation

                                     By:
                                          ------------------------------

                                     Name:
                                            ----------------------------

                                     Title:
                                             ---------------------------


                                       3



<PAGE>

                          CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                         JPMORGAN CHASE BANK,
                                         as Trustee

                                         By:
                                              --------------------------------
                                                  Authorized Officer


                                       4



<PAGE>

                           REVERSE OF 6.8% SENIOR NOTE

         This Security 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 an Indenture, dated as of June 5, 2001, as heretofore supplemented
and amended and as further supplemented by a Second Supplemental Indenture dated
as of February 25, 2003 (collectively, as amended or supplemented from time to
time, herein called the "Indenture", which term shall have the meaning assigned
to it in such instrument), between the Company and JPMorgan Chase Bank (formerly
known as The Chase Manhattan Bank), as Trustee (herein called the "Trustee",
which term includes any successor trustee under the Indenture), and reference is
hereby made to the Indenture for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Company, the
Trustee 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 (the "6.8% Senior Notes") which is
unlimited in aggregate principal amount.

         If an Event of Default with respect to 6.8% Senior Notes shall occur
and be continuing, the principal of the 6.8% Senior Notes may be declared due
and payable in the manner and with the effect provided in the Indenture.

         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 a majority in 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 certain past defaults under
the Indenture and their consequences. Any such consent or waiver by the Holder
of this 6.8% Senior Note shall be conclusive and binding upon such Holder and
upon all future Holders of this 6.8% Senior Note and of any 6.8% Senior Note
issued upon the registration of transfer hereof or in exchange therefor or in
lieu hereof, whether or not notation of such consent or waiver is made upon this
6.8% Senior Note.

         As provided in and subject to the provisions of the Indenture, the
Holder of this 6.8% Senior Note shall not have the right to institute any
proceeding with respect to the Indenture or for the appointment of a receiver or
trustee or for any other remedy thereunder, unless such Holder shall have
previously given the Trustee written notice of a continuing Event of Default
with respect to the 6.8% Senior Notes, the Holders of not less than a majority
in principal amount of the 6.8% Senior Notes at the time Outstanding shall have
made written request to the Trustee to institute proceedings in respect of such
Event of Default as Trustee and offered the Trustee reasonable indemnity, and
the Trustee shall not have received from the Holders of a majority in principal
amount of 6.8% Senior Notes at the time Outstanding a direction inconsistent
with such request, and shall have failed to institute any such proceeding for 60
days after receipt of such notice, request and offer of indemnity. The foregoing
shall not apply to any suit instituted by the Holder of this 6.8% Senior Note
for the enforcement of any payment of

                                       5


<PAGE>

principal hereof or premium, if any, or interest hereon on or after the
respective due dates expressed or provided for herein.

         No reference herein to the Indenture and no provision of this 6.8%
Senior Note or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of, premium,
if any, and interest on this 6.8% Senior Note at the times, place and rate, and
in the coin or currency, herein prescribed.

         As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this 6.8% Senior Note is registrable in the Security
Register, upon surrender of this 6.8% Senior Note for registration of transfer
at the office or agency of the Company in any place where the principal of,
premium, if any, and interest on this 6.8% Senior Note are payable, duly
endorsed by, or accompanied by a written instrument of transfer in form
satisfactory to the Company and the Security Registrar duly executed by, the
Holder hereof or his attorney duly authorized in writing, and thereupon one or
more new 6.8% Senior Notes and of like tenor, of authorized denominations and
for the same aggregate principal amount, will be issued to the designated
transferee or transferees.

         The 6.8% Senior Notes 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,
6.8% Senior Notes are exchangeable for a like aggregate principal amount of 6.8%
Senior Notes having the same Stated Maturity and of like tenor of any authorized
denominations as requested by the Holder upon surrender of the 6.8% Senior Note
or 6.8% Senior Notes to be exchanged at the office or agency of the Company.

         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 6.8% Senior Note 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 this 6.8% Senior Note be overdue, and
neither the Company, the Trustee nor any such agent shall be affected by notice
to the contrary.

         All terms used in this 6.8% Senior Note that are defined in the
Indenture shall have the meanings assigned to them in the Indenture.

                                       6



<PAGE>

                                  ABBREVIATIONS

The following abbreviations, when used in the inscription on the face of this
instrument, shall be construed as though they were written out in full according
to applicable laws or regulations:




TEN COM --                    as tenants in common

TEN ENT --                    as tenants by the entireties

JT TEN --                     as joint tenants with rights of survivorship and
                              not as tenants in common

UNIF GIFT MIN ACT --          ________________________________ Custodian for
                              (Cust)

                              --------------------------------
                              (Minor)

                              Under Uniform Gifts to Minors Act of


                              -------------------------------
                              (State)


     Additional abbreviations may also be used though not on the above list.


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



                                       7

<PAGE>

FOR VALUE RECEIVED, the undersigned hereby sell(s) and transfer(s) unto
____________________ (please insert Social Security or other identifying number
of assignee).

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

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

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


PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING POSTAL ZIP CODE OF
ASSIGNEE

the within 6.8% Senior Note and all rights thereunder, hereby irrevocably
constituting and appointing

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

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

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

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

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

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

agent to transfer said 6.8% Senior Note on the books of the Company, with full
power of substitution in the premises.

Dated: __________________ __, ____


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




NOTICE: The signature to this assignment must correspond with the name as
written upon the face of the within instrument in every particular without
alteration or enlargement, or any change whatever.

                                       8

<PAGE>

                                    EXHIBIT B
                          CERTIFICATE OF AUTHENTICATION

     This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                      JPMORGAN CHASE BANK,
                                      as Trustee

                                      By:
                                           -------------------------------------
                                               Authorized Officer


                                        9