<PAGE>

                                                                     Exhibit 4.8

               FORM OF TRUST PREFERRED SECURITIES AGREEMENT AS TO
                            EXPENSES AND LIABILITIES

         THIS AGREEMENT AS TO EXPENSES AND LIABILITIES (the "Agreement") dated
as of _____________ between MARKEL CORPORATION, a Virginia corporation
("Markel"), and MARKEL CAPITAL TRUST II, a Delaware business trust (the
"Trust").

         WHEREAS, the Trust intends to issue its ___% Common Securities (the
"Common Securities") to, and purchase ___% _____________ Debentures (the
"Debentures") from, Markel Corporation, and to issue and sell its ___% Trust
Preferred Securities (the "Trust Preferred Securities") with such powers,
preferences and special rights and restrictions as are set forth in the Amended
and Restated Trust Agreement of the Trust dated as of _____________, as the same
may be amended from time to time (the "Trust Agreement");

         WHEREAS, Markel Corporation will directly or indirectly own all of the
Common Securities of the Trust and will issue the Debentures;

         NOW, THEREFORE, in consideration of the purchase by each holder of the
Trust Preferred Securities, which purchase Markel Corporation hereby agrees
shall benefit Markel Corporation and which purchase Markel Corporation
acknowledges will be made in reliance upon the execution and delivery of this
Agreement, Markel Corporation and the Trust hereby agree as follows:

                                    ARTICLE I
                         GUARANTEE BY MARKEL CORPORATION

         1.1 Guarantee by Markel Corporation. Subject to the terms and
conditions hereof, Markel Corporation hereby irrevocably and unconditionally
guarantees to each person or entity to whom the Trust is now or hereafter
becomes indebted or liable (the "Beneficiaries") the full payment, when and as
due, of any and all Obligations (as hereinafter defined) to such Beneficiaries.
As used herein, "Obligations" means any costs, expenses or liabilities of the
Trust, other than obligations of the Trust to pay to holders of any Trust
Preferred Securities the amounts due such holders pursuant to the terms of the
Trust Preferred Securities. This Agreement is intended to be for the benefit of,
and to be enforceable by, all such Beneficiaries, whether or not such
Beneficiaries have received notice hereof.

         1.2 Term of Agreement. This Agreement shall terminate and be of no
further force and effect upon the later of (a) the date on which full payment
has been made of all amounts payable to all holders of all the Trust Preferred
Securities (whether upon

<PAGE>

redemption, liquidation, exchange or otherwise) and (b) the date on which there
are no Beneficiaries remaining; provided, however, that this Agreement shall
continue to be effective or shall be reinstated, as the case may be, if at any
time any holder of Trust Preferred Securities or any Beneficiary must restore
payment of any sums paid under the Trust Preferred Securities, under any
Obligation, under the Trust Preferred Securities Guarantee Agreement dated the
date hereof by Markel Corporation and The Chase Manhattan Bank, as guarantee
trustee, or under this Agreement for any reason whatsoever. This Agreement is
continuing, irrevocable, unconditional and absolute.

         1.3 Waiver of Notice. Markel Corporation hereby waives notice of
acceptance of this Agreement and of any Obligation to which it applies or may
apply, and Markel Corporation hereby waives presentment, demand for payment,
protest, notice of nonpayment, notice of dishonor, notice of redemption and all
other notices and demands.

         1.4 No Impairment. The obligations, covenants, agreements and duties of
Markel Corporation under this Agreement shall in no way be affected or impaired
by reason of the happening from time to time of any of the following:

             (a) the extension of time for the payment by the Trust of all or
any portion of the Obligations or for the performance of any other obligation
under, arising out of, or in connection with, the Obligations;

             (b) any failure, omission, delay or lack of diligence on the part
of the Beneficiaries to enforce, assert or exercise any right, privilege, power
or remedy conferred on the Beneficiaries with respect to the Obligations or any
action on the part of the Trust granting indulgence or extension of any kind; or

             (c) 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 Trust or any of the assets of
the Trust.

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

         1.5 Enforcement. A Beneficiary may enforce this Agreement directly
against Markel Corporation, and Markel Corporation waives any right or remedy to
require that any action be brought against the Trust or any other person or
entity before proceeding against Markel Corporation.

         1.6 Subrogation. Markel Corporation shall be subrogated to all rights
(if any) of the Trust in respect of any amounts paid to the Beneficiaries by
Markel Corporation under this Agreement; provided, however, that Markel
Corporation shall not (except to the extent required by mandatory provisions of
law) be entitled to enforce or exercise any rights which it may acquire by way
of subrogation or any indemnity, reimbursement or


                                       -2-

<PAGE>

other agreement, in all cases as a result of payment under this Agreement, if,
at the time of any such payment, any amounts are due and unpaid under this
Agreement.

                                   ARTICLE II
                                 BINDING EFFECT

         2.1 Binding Effect. All guarantees and agreements contained in this
Agreement shall bind the successors, assigns, receivers, trustees and
representatives of Markel Corporation and shall inure to the benefit of the
Beneficiaries.

         2.2 Amendment. So long as there remains any Beneficiary or any Trust
Preferred Securities outstanding, this Agreement shall not be modified or
amended in any manner adverse to such Beneficiary or to the holders of the Trust
Preferred Securities.

         2.3 Notices. Any notice, request or other communication required or
permitted to be given hereunder shall be given in writing by delivering the same
by personal delivery, by facsimile transmission or by first-class mail,
addressed as follows (and if so given, shall be deemed given when so delivered,
upon receipt of confirmation if by facsimile, or three days after mailed if by
first-class mail):

             If to the Trust to:

                      Markel Capital Trust II
                      c/o Markel Corporation
                      4521 Highwoods Parkway
                      Glen Allen, Virginia 23060-6148
                      Fax: (804) 527-3810

             with a copy to:

                      Markel Corporation
                      4521 Highwoods Parkway
                      Glen Allen, Virginia 23060-6148
                      Fax: (804) 527-3810

         2.4 Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED
AND INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK (WITHOUT
REGARD TO CONFLICT OF LAWS PRINCIPLES).


                                       -3-

<PAGE>

         THIS AGREEMENT is executed as of the day and year first above written.

                                MARKEL CORPORATION



                                By:      ___________________________________
                                Name:
                                Title:



                                MARKEL CAPITAL TRUST II



                                By:      ___________________________________
                                         as Administrative Trustee

                                By:      ___________________________________
                                         as Administrative Trustee





                                       -4-