<Page>

                                                                 EXHIBIT 10.5.2

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


                          FIRST SUPPLEMENTAL INDENTURE

                            Dated as of May 19, 2003

                                     among

                         FUND AMERICAN COMPANIES, INC.,
                     WHITE MOUNTAINS INSURANCE GROUP, LTD.

                                      and

                        BANK ONE, NATIONAL ASSOCIATION,

                                   AS TRUSTEE

                       Supplementing the Senior Indenture
                            Dated as of May 19, 2003


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

<Page>

     FIRST SUPPLEMENTAL INDENTURE, dated as of May 19, 2003 (the "SUPPLEMENTAL
INDENTURE"), by and among FUND AMERICAN COMPANIES, INC., a Delaware corporation
(the "COMPANY") having its principal office at 370 Church Street, Guilford,
Connecticut 06437, WHITE MOUNTAINS INSURANCE GROUP, LTD., a company existing
under the laws of Bermuda, as Guarantor (the "GUARANTOR"), having its principal
office at 80 South Main Street, Hanover, New Hampshire 03755-2053, and Bank One,
National Association, as trustee (the "TRUSTEE").

     WHEREAS, the Company and the Guarantor executed and delivered the Indenture
to the Trustee to provide for the future issuance of its Securities, to be
issued from time to time in one or more series as might be determined by the
Company under the Indenture, in an unlimited aggregate principal amount which
may be authenticated and delivered thereunder as in the Indenture provided;

     WHEREAS, pursuant to the terms of the Indenture, the Company desires to
provide for the establishment of a new series of its Securities to be known as
its 5.875% Senior Notes due 2013 (the "NOTES"), the form of such Notes and the
terms, provisions and conditions thereof to be as provided in the Indenture and
this First Supplemental Indenture; and

     WHEREAS, the Company and the Guarantor desire and have requested the
Trustee to join with them in the execution and delivery of this First
Supplemental Indenture, and all requirements necessary to make this First
Supplemental Indenture a valid instrument, enforceable in accordance with its
terms, and to make the Notes, when executed by the Company and authenticated and
delivered by the Trustee, and the Guarantees endorsed thereon, when executed by
the Guarantor, the legal, valid and binding obligations of the Company and the
Guarantor, as the case may be, have been performed and fulfilled, and the
execution and delivery of this First Supplemental Indenture and the Notes have
been in all respects duly authorized.

     NOW, THEREFORE, in consideration of the purchase and acceptance of the
Notes by the holders thereof, and for the purpose of setting forth, as provided
in the Indenture, the form of the Notes and the terms, provisions and conditions
thereof, the Company and the Guarantor, as the case may be, covenant and agree
with the Trustee as follows:

                                   ARTICLE 1
                   GENERAL TERMS AND CONDITIONS OF THE NOTES

     Section 1.01. There shall be and are hereby authorized a series of
Securities designated the "5.875% Senior Notes due 2013".

     Section 1.02. The Notes shall be initially limited in aggregate principal
amount to $700,000,000. Without the consent of the Holders of the Notes, the
aggregate principal amount of the Notes may be increased in the future, on the
same terms and conditions and with the same CUSIP number as the Notes have, so
that such additional notes and the

                                        1
<Page>

outstanding Notes shall form a single series of Securities under the Indenture
as supplemented by this Supplemental Indenture. The Notes shall mature and the
principal thereof shall be due and payable, together with all accrued and unpaid
interest thereon on May 15, 2013.

     Section 1.03. The Notes shall be initially issued as Global Securities.
Principal and interest on the Notes issued in certificated form will be payable,
the transfer of such Notes will be registrable and such Notes will be
exchangeable for Notes bearing identical terms and provisions at the office or
agency of the Company in the Borough of Manhattan, The City and State of New
York provided for that purpose and transfers of the Notes will also be
registrable at any of the Company's other offices or agencies as the Company may
maintain for that purpose; provided, however, that payment of interest may be
made at the option of the Company by check mailed to the registered holder at
such address as shall appear in the Security Register and that the payment of
principal with respect to the Notes will only be made upon surrender of the
Notes to the Trustee.

     Section 1.04. (a) Each Note will bear interest at a rate of 5.875% per
annum from May 19, 2003 until the principal thereof becomes due and payable,
payable semi-annually in arrears on May 15 and November 15 of each year (each,
an "INTEREST PAYMENT DATE", commencing on November 15, 2003), to the person in
whose name such Note (or one or more Predecessor Securities) is registered at
the close of business on the Regular Record Date for such interest installment,
which, except as set forth below, shall be the May 1 or November 1, as the case
may be, preceding the Interest Payment Date with respect to such interest
installment.

     (b)  Any installment of interest not punctually paid or duly provided for
shall forthwith cease to be payable to the registered holder of a Note on such
Regular Record Date and may be paid to the person in whose name such Note (or
one or more Predecessor Securities) is registered at the close of business on a
Special Record Date to be fixed by the Trustee for the payment of such defaulted
interest, notice whereof to be given to the registered holders of the Notes not
less than 10 days prior to such Special Record Date, or may be paid at any time
in any other lawful manner not inconsistent with the requirements of any
securities exchange on which the Notes may be listed, and upon such notice as
may be required by such exchange, all as more fully provided in the Indenture.

     (c)  The amount of interest payable for any period will be computed on the
basis of a 360-day year consisting of twelve 30-day months. In the event that
any date on which interest is payable on the Notes is not a Business Day, then
payment of 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).

     Section 1.05. The Notes are not entitled to any sinking fund.

                                        2
<Page>

                                   ARTICLE 2
                        OPTIONAL REDEMPTION OF THE NOTES

     Section 2.01. The Notes will be redeemable as a whole at any time or in
part from time to time, at the option of the Company, at a redemption price
equal to the greater of (i) 100% of the principal amount of the Notes being
redeemed or (ii) the sum of the present values of the remaining scheduled
payments of principal and interest (other than accrued interest) on the Notes
being redeemed, discounted to the redemption date on a semiannual basis
(assuming a 360-day year consisting of twelve 30-day months) at the Treasury
Rate (as defined below) plus 50 basis points plus, in either case, any interest
accrued but not paid to the date of redemption. Notice of any redemption will be
mailed at least 30 days but no more than 60 days before the redemption date to
each holder of the Notes to be redeemed. Unless the Company defaults in payment
of the redemption price, on and after the redemption date interest will cease to
accrue on the Notes or portions thereof called for redemption. The Notes will
not be subject to any sinking fund provision.

     "TREASURY RATE" means, with respect to any redemption date for the Notes,
the rate per year equal to the semi-annual equivalent yield to maturity of the
Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue
(expressed as a percentage of its principal amount) equal to the Comparable
Treasury Price for the redemption date.

     "COMPARABLE TREASURY ISSUE" means the United States Treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining term of the Notes to be redeemed that would be utilized, at the
time of selection and in accordance with customary financial practice, in
pricing new issues of corporate debt securities of comparable maturity to the
remaining term of such Notes.

     "INDEPENDENT INVESTMENT BANKER" means one of the Reference Treasury Dealers
appointed by the Company after consultation with the Trustee.

     "COMPARABLE TREASURY PRICE" means, with respect to any redemption date for
the Notes, (1) the average of the bid and asked prices for the Comparable
Treasury Issue (expressed in each case as a percentage of its principal amount)
on the third business day preceding the redemption date, as set forth in the
daily statistical release (or any successor release) published by the Federal
Reserve Bank of New York and designated "Composite 3:30 p.m. Quotations for U.S.
Government Securities" or (2) if that release (or any successor release) is not
published or does not contain those prices on that business day, (A) the average
of the Reference Treasury Dealer Quotations for the redemption date, after
excluding the highest and lowest Reference Treasury Dealer Quotations for that
redemption date, or (B) if the Company obtains fewer than four Reference
Treasury Dealer Quotations, the average of all the Reference Treasury Dealer
Quotations obtained.

     "REFERENCE TREASURY DEALER" means (1) each of Lehman Brothers Inc., Banc of
America Securities LLC and Credit Suisse First Boston LLC and, in each case,
their respective successors; provided, however, that if any of them ceases to be
a primary U.S.

                                        3
<Page>

Government securities dealer in New York City, the Company shall appoint another
primary U.S. Government securities dealer as a substitute and (2) any other U.S.
Government securities dealers selected by the Company.

     "REFERENCE TREASURY DEALER QUOTATIONS" means, with respect to each
Reference Treasury Dealer and any redemption date, the average, as determined by
the Trustee, of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount) quoted in
writing to the Trustee by such Reference Treasury Dealer at 5:00 p.m. New York
City time on the third Business Day preceding such redemption date.

                                   ARTICLE 3
                                   AMENDMENTS

     Section 3.01. Section 501(4) of the Indenture is hereby amended, solely
with respect to the Notes, by deleting the number "90" and substituting in its
place the number "60".

     Section 3.02. Section 501 of the Indenture is hereby amended, solely with
respect to the Notes, by adding the following new additional Event of Default
pursuant to Section 501(8):

default under any mortgage, indenture or instrument evidencing or securing Debt
for money borrowed by the Company or the Guarantor or any of their respective
Subsidiaries, whether such Debt or guarantee now exists, or is created after the
date of this Indenture, which default results in the acceleration of the payment
of such Debt or constitutes the failure to pay the principal of such Debt when
due (after giving effect to any applicable grace period provided in such Debt)
(a "PAYMENT DEFAULT") and, in each case, the total amount of any such Debt has
an aggregate principal amount greater than $25.0 million.

     Section 3.03. Section 602 of the Indenture is hereby amended, solely with
respect to the Notes, by deleting both of the numbers "90" and substituting in
their place the numbers "60".

     Section 3.04. Section 1006 of the Indenture is hereby amended, solely with
respect to the Notes, by deleting the number "15%" in the second paragraph and
substituting in its place the number "10%".

     Section 3.05. Section 1007 of the Indenture is hereby amended, solely with
respect to the Notes, by deleting the word "five" in clause (ii) of the first
sentence and substituting in its place the word "three".

                                        4
<Page>

                                   ARTICLE 4
                               FORM OF THE NOTES

     Section 4.01. The Notes are to be issued on two certificates substantially
in the form of Exhibits A and B, respectively. The Trustee's Certificate of
Authentication to be endorsed thereon and the Notation of Guarantee of the
Securities shall be substantially in the form set forth in Sections 203 and 205
of the Indenture, respectively.

                                   ARTICLE 5
                          ORIGINAL ISSUE OF THE NOTES

     Section 5.01. The Notes in the initial aggregate principal amount equal to
$700,000,000, may, upon execution of this First Supplemental Indenture, be
executed by the Company, with the Guarantee endorsed thereon executed by the
Guarantor, and delivered to the Trustee for authentication, and the Trustee
shall thereupon authenticate and make available for delivery the said Notes to
or upon a Company Order.

                                   ARTICLE 6
                            MISCELLANEOUS PROVISIONS

     Section 6.01. Except as otherwise expressly provided in this First
Supplemental Indenture or in the form of the Notes or otherwise clearly required
by the context hereof or thereof, all terms used herein or in said form of the
Notes that are defined in the Indenture shall have the several meanings
respectively assigned to them therein.

     Section 6.02. The Indenture, as supplemented by this First Supplemental
Indenture, is in all respects ratified and confirmed. This First Supplemental
Indenture shall be deemed part of the Indenture in the manner and to the extent
herein and therein provided.

     Section 6.03. The recitals herein contained are made by the Company and not
by the Trustee, and the Trustee assumes no responsibility for the correctness
thereof. The Trustee makes no representation as to the validity or sufficiency
of this First Supplemental Indenture.

     Section 6.04. This First Supplemental Indenture 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.

                            [SIGNATURE PAGE FOLLOWS]

                                        5
<Page>

     IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental
Indenture to be duly executed as of the day and year first above written.

                                                  FUND AMERICAN COMPANIES, INC.


                                                  By:  /s/ Kernan V. Oberting
                                                       -------------------------
                                                       Name:  Kernan V. Oberting
                                                       Title: Vice President


                                                  WHITE MOUNTAINS INSURANCE
                                                    GROUP, LTD., as Guarantor


                                                  By:  /s/ Dennis Beaulieu
                                                       -------------------------
                                                       Name:  Dennis Beaulieu
                                                       Title: Secretary


                                                  BANK ONE, NATIONAL
                                                    ASSOCIATION, as Trustee


                                                  By:  /s/ Mary R. Fonti
                                                       -------------------------
                                                       Name:  Mary R. Fonti
                                                       Title: Vice President

                                        6
<Page>

                                    Exhibit A

                    Form of the 5.875% Senior Notes due 2013

          UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE COMPANY
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
IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO., OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC) ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

          UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR THE
INDIVIDUAL SECURITIES REPRESENTED HEREBY, THIS GLOBAL SECURITY MAY NOT BE
TRANSFERRED EXCEPT AS A WHOLE BY DTC TO A NOMINEE OF DTC OR BY A NOMINEE OF DTC
TO DTC OR ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A SUCCESSOR
DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

                                       A-1
<Page>

                                                             CUSIP No. 36077BAA5
                                                                    $350,000,000

No.001

                           5.875% Senior Note due 2013

          Fund American Companies, Inc., a Delaware corporation, promises to pay
to Cede & Co., or registered assigns, the principal sum of THREE HUNDRED AND
FIFTY MILLION Dollars on May 15, 2013.

          Interest Payment Dates: May 15 and November 15, commencing November
15, 2003.

          Record Dates: May 1 and November 1.
          Additional provisions of this Security are set forth on the reverse
side of this Security.

                                       A-2
<Page>

Dated:  May 19, 2003

                                              FUND AMERICAN COMPANIES, INC.
                                               by

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

                                       A-3
<Page>

                              NOTATION OF GUARANTEE

          White Mountains Insurance Group, Ltd., a company existing under the
law of Bermuda (the "Guarantor", which term includes any successor thereto under
the Indenture (the "Indenture") referred to in the Security on which this
notation is endorsed) has unconditionally guaranteed, pursuant to the terms of
the Guarantee contained in Article Twelve of the Indenture, the due and punctual
payment of the principal of and any premium and interest on this Security, when
and as the same shall become due and payable, whether at the Stated Maturity, by
declaration of acceleration, call for redemption, early repayment or otherwise,
in accordance with the terms of this Security and the Indenture.

          The obligations of the Guarantor to the Holders of the Securities and
to the Trustee pursuant to the Guarantee and the Indenture are expressly set
forth in Article Twelve of the Indenture, and reference is hereby made to such
Article and Indenture for the precise terms of the Guarantee.

          The Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication on the Security upon which this notation of
the Guarantee is endorsed shall have been executed by the Trustee under the
Indenture by the manual signature of one of its authorized signatories.

                                       A-4
<Page>

Dated: May 19, 2003

                                           WHITE MOUNTAINS INSURANCE GROUP, LTD.
                                            by

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

                                       A-5
<Page>

                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

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

Dated: May 19, 2003

                                                BANK ONE, NATIONAL
                                                ASSOCIATION
                                                 as Trustee,

                                                 by

                                                 -------------------------------
                                                 Authorized Signatory

                                       A-6
<Page>

                           5.875% Senior Note due 2013

                               REVERSE OF SECURITY

1. INTEREST
          Fund American Companies, Inc., a Delaware corporation (such
corporation, and its successors and assigns under the Indenture hereinafter
referred to, being herein called the "Company"), promises to pay interest on the
principal amount of this Security at the rate per annum shown above. The Company
will pay interest semiannually in arrears on May 15 and November 15 of each
year, commencing November 15, 2003. Interest on the Securities will accrue from
the most recent date to which interest has been paid or, if no interest has been
paid, from May 19, 2003. Interest will be computed on the basis of a 360-day
year comprised of twelve 30-day months.

          The Company shall pay interest on overdue principal and premium, if
any, and interest on overdue installments of interest, to the extent lawful, at
the same rate per annum payable on the principal of this Security.

2. METHOD OF PAYMENT
          The Company will pay interest on the Securities (except overdue
interest) to the Persons who are registered Holders of Securities at the close
of business on May 1 or November 1 next preceding the Interest Payment Date even
if Securities are canceled after the Regular Record Date and on or before the
Interest Payment Date. Holders must surrender Securities to a Paying Agent to
collect principal payments. The Company will pay principal and interest in money
of the United States that at the time of payment is legal tender for payment of
public and private debts. Payments in respect of the Securities represented by a
Global Security (including principal, premium, if any, and interest) will be
made by wire transfer of immediately available funds to the accounts specified
by The Depository Trust Company. The Company will make all payments in respect
of a certificated Security (including principal, premium, if any, and interest)
by mailing a check to the registered address of each Holder thereof; provided,
however, that payments on a certificated Security will be made by wire transfer
to a U.S. dollar account maintained by the payee with a bank in the United
States if such Holder elects payment by wire transfer by giving written notice
to the Trustee or the Paying Agent to such effect designating such account no
later than 30 days immediately preceding the relevant due date for payment (or
such other date as the Trustee may accept in its discretion).

3. PAYING AGENT AND REGISTRAR
          Initially, Bank One, National Association (the "Trustee"), will act as
Paying Agent and Registrar. The Company may appoint and change any Paying Agent,
Registrar or co-Registrar without notice. The Company or any of its domestically
incorporated Wholly Owned Subsidiaries may act as Paying Agent, Registrar or
co-Registrar.

4. INDENTURE
          The Company issued the Securities under an Indenture dated as of May
19, 2003, as supplemented by the First Supplemental Indenture dated as of May
19, 2003

                                       A-7
<Page>

(together, the "Indenture"), among the Company, the Guarantor and the Trustee.
The terms of the Securities include those stated in the Indenture and those made
part of the Indenture by reference to the Trust Indenture Act of 1939 (15 U.S.C.
Sections 77aaa-77bbbb) as in effect on the date of the Indenture (the "TIA").
Terms defined in the Indenture and not defined herein have the meanings ascribed
thereto in the Indenture. The Securities are subject to all such terms, and
Securityholders are referred to the Indenture and the TIA for a statement of
those terms. To the extent permitted by applicable law, in the event of any
inconsistency between the terms of this Security and the terms of the Indenture,
the terms of the Indenture shall control.

          The Securities are general unsecured obligations of the Company. The
Indenture contains covenants that limit the ability of the Company and its
Subsidiaries to grant Liens; enter into Sale/Leaseback Transactions; and
consolidate, merge or transfer all or substantially all of its assets and the
assets of its Subsidiaries. These covenants are subject to important exceptions
and qualifications set forth in the Indenture.

5. OPTIONAL REDEMPTION
          The Securities are redeemable as a whole at any time or in part from
time to time, at the option of the Company, at a redemption price equal to the
greater of (i) 100% of the principal amount of such Securities or (ii) the sum
of the present values of the remaining scheduled payments of principal and
interest (other than accrued interest) on the Securities being redeemed,
discounted to the redemption date on a semi-annual basis (assuming a 360-day
year consisting of twelve 30-day months) at the Treasury Rate plus 50 basis
points plus, in either case, any interest accrued but not paid to the date of
redemption.

6. NOTICE OF REDEMPTION
          Notice of redemption shall be given by first-class mail, postage
prepaid, mailed not less than 30 nor more than 60 days prior to the redemption
date, to each holder of Securities to be redeemed, at his address appearing in
the Security Register. Unless the Company defaults in payment of the redemption
price, on and after the redemption date interest will cease to accrue on the
Securities or portions thereof called for redemption.

7. GUARANTEE
          The payment by the Company of the principal of, and premium and
interest on, the Securities is irrevocably and unconditionally guaranteed on a
senior basis by the Guarantor.

8. DENOMINATIONS; TRANSFER; EXCHANGE
          The Securities are in registered form in denominations of $1,000
principal amount and integral multiples of $1,000. A Holder may transfer or
exchange Securities in accordance with the Indenture. The Company may require a
Holder, among other things, to furnish appropriate endorsements or transfer
documents and to pay any taxes or other governmental charge that may be imposed
in connection with any transfer or exchange of Securities or permitted by the
Indenture. The Company need not issue, transfer or exchange any Security of any
series during a period beginning at the opening

                                       A-8
<Page>

of business 15 days before the day of the mailing of a notice of redemption of
Securities of such series selected for redemption and ending at the close of
business on the date of such mailing, or transfer or exchange any Security
selected for redemption in whole or in part, except for the portion of such
Security not selected for redemption.

9. PERSONS DEEMED OWNERS
          The person in whose name any Security is registered in the Security
Register may be treated as the owner of it for all purposes.

10. UNCLAIMED MONEY
          The Trustee and any paying agent shall pay to the Company or the
Guarantor upon request any money held by them for the payment of principal,
premium or interest that remains unclaimed for two years, and, thereafter,
Holders entitled to such money must look to the Company or the Guarantor for
payment as general creditors and all liability of the Trustee or such paying
agent with respect to such money shall thereupon cease.

11. DISCHARGE AND DEFEASANCE
          Subject to certain conditions, the Company at any time shall be
entitled to terminate some or all of its obligations under the Securities and
the Indenture if the Company or the Guarantor irrevocably deposits with the
Trustee money or U.S. Government Obligations for the payment of principal and
interest on the Securities to maturity or redemption, as the case may be.

12. AMENDMENT, WAIVER
          Subject to certain exceptions, the Indenture or the Securities may be
amended or supplemented with the consent of the Holders of not less than a
majority in principal amount of the Outstanding Securities, and any past default
or compliance with any covenant or condition may be waived with the consent of
the Holders of at least a majority in principal amount of the Securities then
Outstanding. Without notice to or the consent of any Holder, the parties thereto
may supplement the Indenture to, among other things, cure any ambiguity, correct
or supplement any inconsistency or make any other provisions with respect to
matters or questions arising thereunder, provided that such change does not
adversely affect the interest of any Holder.

13. DEFAULTS AND REMEDIES
          The events of default and remedies specified in the Indenture apply to
the Securities. If an Event of Default, as defined in the Indenture, occurs and
is continuing, the Trustee or the Holders of not less than 25% in aggregate
principal amount of the Securities then Outstanding may declare all the
Securities to be due and payable. Holders may not enforce the Indenture or the
Securities except as provided in the Indenture. The Trustee may require
indemnity satisfactory to it before it enforces the Indenture or the Securities.
Subject to certain limitations, Holders of a majority in principal amount of the
Outstanding Securities may direct the Trustee in its exercise of any trust or
power.

                                       A-9
<Page>

14. TRUSTEE DEALINGS WITH THE COMPANY
          Subject to certain limitations imposed by the TIA, the Trustee under
the Indenture, in its individual or any other capacity, may become the owner or
pledgee of Securities and may otherwise deal with and collect obligations owed
to it by the Company or its Affiliates and may otherwise deal with the Company
or its Affiliates with the same rights it would have if it were not the Trustee.

15. BENEFITS OF INDENTURE
          Nothing in the Indenture or in the Securities, express or implied,
shall give to any Person, other than the Company, the Guarantor, the Trustee and
their successors thereunder, any Authenticating Agent or Paying Agent, the
Security Registrar and the Holders of Securities (or such of them as may be
affected thereby), any benefit or any legal or equitable right, remedy or claim
under the Indenture.

16. AUTHENTICATION
          This Security shall not be valid until an authorized signatory of the
Trustee (or an authenticating agent) manually signs the certificate of
authentication on the other side of this Security.

17. ABBREVIATIONS
          Customary abbreviations may be used in the name of a Securityholder or
an assignee, such as TEN COM (=tenants in common), TEN ENT (=tenants by the
entireties), JT TEN (=joint tenants with rights of survivorship and not as
tenants in common), CUST (=custodian), and U/G/M/A (=Uniform Gift to Minors
Act).

18. CUSIP NUMBERS
          Pursuant to a recommendation promulgated by the Committee on Uniform
Security Identification Procedures the Company has caused CUSIP numbers to be
printed on the Securities and has directed the Trustee to use CUSIP numbers in
notices of redemption as a convenience to Securityholders. No representation is
made as to the accuracy of such numbers either as printed on the Securities or
as contained in any notice of redemption and reliance may be placed only on the
other identification numbers placed thereon.

19. GOVERNING LAW
          THIS SECURITY SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY
THE LAWS OF THE STATE OF NEW YORK.

          The Company will furnish to any Securityholder upon written request
and without charge to the Securityholder a copy of the Indenture. Requests may
be made to:

          White Mountains Insurance Group, Ltd.
          80 South Main Street
          Hanover, NH 03755-2053
          Attention: General Counsel

                                      A-10
<Page>

                                    Exhibit B

                    Form of the 5.875% Senior Notes due 2013

          UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE COMPANY
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
IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO., OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC) ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

          UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR THE
INDIVIDUAL SECURITIES REPRESENTED HEREBY, THIS GLOBAL SECURITY MAY NOT BE
TRANSFERRED EXCEPT AS A WHOLE BY DTC TO A NOMINEE OF DTC OR BY A NOMINEE OF DTC
TO DTC OR ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A SUCCESSOR
DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

                                       B-1
<Page>

                                                             CUSIP No. 36077BAA5
                                                                    $350,000,000

No.002

                           5.875% Senior Note due 2013

          Fund American Companies, Inc., a Delaware corporation, promises to pay
to Cede & Co., or registered assigns, the principal sum of THREE HUNDRED AND
FIFTY MILLION Dollars on May 15, 2013.

          Interest Payment Dates: May 15 and November 15, commencing November
15, 2003.

          Record Dates: May 1 and November 1.
          Additional provisions of this Security are set forth on the reverse
side of this Security.

                                       B-2
<Page>

Dated: May 19, 2003

                                               FUND AMERICAN COMPANIES, INC.
                                                by

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

                                       B-3
<Page>

                              NOTATION OF GUARANTEE

          White Mountains Insurance Group, Ltd., a company existing under the
law of Bermuda (the "Guarantor", which term includes any successor thereto under
the Indenture (the "Indenture") referred to in the Security on which this
notation is endorsed) has unconditionally guaranteed, pursuant to the terms of
the Guarantee contained in Article Twelve of the Indenture, the due and punctual
payment of the principal of and any premium and interest on this Security, when
and as the same shall become due and payable, whether at the Stated Maturity, by
declaration of acceleration, call for redemption, early repayment or otherwise,
in accordance with the terms of this Security and the Indenture.

          The obligations of the Guarantor to the Holders of the Securities and
to the Trustee pursuant to the Guarantee and the Indenture are expressly set
forth in Article Twelve of the Indenture, and reference is hereby made to such
Article and Indenture for the precise terms of the Guarantee.

          The Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication on the Security upon which this notation of
the Guarantee is endorsed shall have been executed by the Trustee under the
Indenture by the manual signature of one of its authorized signatories.

                                       B-4
<Page>

Dated: May 19, 2003

                                           WHITE MOUNTAINS INSURANCE GROUP, LTD.
                                            by

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

                                       B-5
<Page>

                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

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

Dated: May 19, 2003

                                                       BANK ONE, NATIONAL
                                                       ASSOCIATION
                                                        as Trustee,

                                                        by

                                                        ------------------------
                                                        Authorized Signatory

                                       B-6
<Page>

                           5.875% Senior Note due 2013

                               REVERSE OF SECURITY

1. INTEREST
          Fund American Companies, Inc., a Delaware corporation (such
corporation, and its successors and assigns under the Indenture hereinafter
referred to, being herein called the "Company"), promises to pay interest on the
principal amount of this Security at the rate per annum shown above. The Company
will pay interest semiannually in arrears on May 15 and November 15 of each
year, commencing November 15, 2003. Interest on the Securities will accrue from
the most recent date to which interest has been paid or, if no interest has been
paid, from May 19, 2003. Interest will be computed on the basis of a 360-day
year comprised of twelve 30-day months.

          The Company shall pay interest on overdue principal and premium, if
any, and interest on overdue installments of interest, to the extent lawful, at
the same rate per annum payable on the principal of this Security.

2. METHOD OF PAYMENT
          The Company will pay interest on the Securities (except overdue
interest) to the Persons who are registered Holders of Securities at the close
of business on May 1 or November 1 next preceding the Interest Payment Date even
if Securities are canceled after the Regular Record Date and on or before the
Interest Payment Date. Holders must surrender Securities to a Paying Agent to
collect principal payments. The Company will pay principal and interest in money
of the United States that at the time of payment is legal tender for payment of
public and private debts. Payments in respect of the Securities represented by a
Global Security (including principal, premium, if any, and interest) will be
made by wire transfer of immediately available funds to the accounts specified
by The Depository Trust Company. The Company will make all payments in respect
of a certificated Security (including principal, premium, if any, and interest)
by mailing a check to the registered address of each Holder thereof; provided,
however, that payments on a certificated Security will be made by wire transfer
to a U.S. dollar account maintained by the payee with a bank in the United
States if such Holder elects payment by wire transfer by giving written notice
to the Trustee or the Paying Agent to such effect designating such account no
later than 30 days immediately preceding the relevant due date for payment (or
such other date as the Trustee may accept in its discretion).

3. PAYING AGENT AND REGISTRAR
          Initially, Bank One, National Association (the "Trustee"), will act as
Paying Agent and Registrar. The Company may appoint and change any Paying Agent,
Registrar or co-Registrar without notice. The Company or any of its domestically
incorporated Wholly Owned Subsidiaries may act as Paying Agent, Registrar or
co-Registrar.

4. INDENTURE
          The Company issued the Securities under an Indenture dated as of May
19, 2003, as supplemented by the First Supplemental Indenture dated as of May
19, 2003

                                       B-7
<Page>

(together, the "Indenture"), among the Company, the Guarantor and the Trustee.
The terms of the Securities include those stated in the Indenture and those made
part of the Indenture by reference to the Trust Indenture Act of 1939 (15 U.S.C.
Sections 77aaa-77bbbb) as in effect on the date of the Indenture (the "TIA").
Terms defined in the Indenture and not defined herein have the meanings ascribed
thereto in the Indenture. The Securities are subject to all such terms, and
Securityholders are referred to the Indenture and the TIA for a statement of
those terms. To the extent permitted by applicable law, in the event of any
inconsistency between the terms of this Security and the terms of the Indenture,
the terms of the Indenture shall control.

          The Securities are general unsecured obligations of the Company. The
Indenture contains covenants that limit the ability of the Company and its
Subsidiaries to grant Liens; enter into Sale/Leaseback Transactions; and
consolidate, merge or transfer all or substantially all of its assets and the
assets of its Subsidiaries. These covenants are subject to important exceptions
and qualifications set forth in the Indenture.

5. OPTIONAL REDEMPTION
          The Securities are redeemable as a whole at any time or in part from
time to time, at the option of the Company, at a redemption price equal to the
greater of (i) 100% of the principal amount of such Securities or (ii) the sum
of the present values of the remaining scheduled payments of principal and
interest (other than accrued interest) on the Securities being redeemed,
discounted to the redemption date on a semi-annual basis (assuming a 360-day
year consisting of twelve 30-day months) at the Treasury Rate plus 50 basis
points plus, in either case, any interest accrued but not paid to the date of
redemption.

6. NOTICE OF REDEMPTION
          Notice of redemption shall be given by first-class mail, postage
prepaid, mailed not less than 30 nor more than 60 days prior to the redemption
date, to each holder of Securities to be redeemed, at his address appearing in
the Security Register. Unless the Company defaults in payment of the redemption
price, on and after the redemption date interest will cease to accrue on the
Securities or portions thereof called for redemption.

7. GUARANTEE
          The payment by the Company of the principal of, and premium and
interest on, the Securities is irrevocably and unconditionally guaranteed on a
senior basis by the Guarantor.

8. DENOMINATIONS; TRANSFER; EXCHANGE
          The Securities are in registered form in denominations of $1,000
principal amount and integral multiples of $1,000. A Holder may transfer or
exchange Securities in accordance with the Indenture. The Company may require a
Holder, among other things, to furnish appropriate endorsements or transfer
documents and to pay any taxes or other governmental charge that may be imposed
in connection with any transfer or exchange of Securities or permitted by the
Indenture. The Company need not issue, transfer or exchange any Security of any
series during a period beginning at the opening

                                       B-8
<Page>

of business 15 days before the day of the mailing of a notice of redemption of
Securities of such series selected for redemption and ending at the close of
business on the date of such mailing, or transfer or exchange any Security
selected for redemption in whole or in part, except for the portion of such
Security not selected for redemption.

9. PERSONS DEEMED OWNERS
          The person in whose name any Security is registered in the Security
Register may be treated as the owner of it for all purposes.

10. UNCLAIMED MONEY
          The Trustee and any paying agent shall pay to the Company or the
Guarantor upon request any money held by them for the payment of principal,
premium or interest that remains unclaimed for two years, and, thereafter,
Holders entitled to such money must look to the Company or the Guarantor for
payment as general creditors and all liability of the Trustee or such paying
agent with respect to such money shall thereupon cease.

11. DISCHARGE AND DEFEASANCE
          Subject to certain conditions, the Company at any time shall be
entitled to terminate some or all of its obligations under the Securities and
the Indenture if the Company or the Guarantor irrevocably deposits with the
Trustee money or U.S. Government Obligations for the payment of principal and
interest on the Securities to maturity or redemption, as the case may be.

12. AMENDMENT, WAIVER
          Subject to certain exceptions, the Indenture or the Securities may be
amended or supplemented with the consent of the Holders of not less than a
majority in principal amount of the Outstanding Securities, and any past default
or compliance with any covenant or condition may be waived with the consent of
the Holders of at least a majority in principal amount of the Securities then
Outstanding. Without notice to or the consent of any Holder, the parties thereto
may supplement the Indenture to, among other things, cure any ambiguity, correct
or supplement any inconsistency or make any other provisions with respect to
matters or questions arising thereunder, provided that such change does not
adversely affect the interest of any Holder.

13. DEFAULTS AND REMEDIES
          The events of default and remedies specified in the Indenture apply to
the Securities. If an Event of Default, as defined in the Indenture, occurs and
is continuing, the Trustee or the Holders of not less than 25% in aggregate
principal amount of the Securities then Outstanding may declare all the
Securities to be due and payable. Holders may not enforce the Indenture or the
Securities except as provided in the Indenture. The Trustee may require
indemnity satisfactory to it before it enforces the Indenture or the Securities.
Subject to certain limitations, Holders of a majority in principal amount of the
Outstanding Securities may direct the Trustee in its exercise of any trust or
power.

                                       B-9
<Page>

14. TRUSTEE DEALINGS WITH THE COMPANY
          Subject to certain limitations imposed by the TIA, the Trustee under
the Indenture, in its individual or any other capacity, may become the owner or
pledgee of Securities and may otherwise deal with and collect obligations owed
to it by the Company or its Affiliates and may otherwise deal with the Company
or its Affiliates with the same rights it would have if it were not the Trustee.

15. BENEFITS OF INDENTURE
          Nothing in the Indenture or in the Securities, express or implied,
shall give to any Person, other than the Company, the Guarantor, the Trustee and
their successors thereunder, any Authenticating Agent or Paying Agent, the
Security Registrar and the Holders of Securities (or such of them as may be
affected thereby), any benefit or any legal or equitable right, remedy or claim
under the Indenture.

16. AUTHENTICATION
          This Security shall not be valid until an authorized signatory of the
Trustee (or an authenticating agent) manually signs the certificate of
authentication on the other side of this Security.

17. ABBREVIATIONS
          Customary abbreviations may be used in the name of a Securityholder or
an assignee, such as TEN COM (=tenants in common), TEN ENT (=tenants by the
entireties), JT TEN (=joint tenants with rights of survivorship and not as
tenants in common), CUST (=custodian), and U/G/M/A (=Uniform Gift to Minors
Act).

18. CUSIP NUMBERS
          Pursuant to a recommendation promulgated by the Committee on Uniform
Security Identification Procedures the Company has caused CUSIP numbers to be
printed on the Securities and has directed the Trustee to use CUSIP numbers in
notices of redemption as a convenience to Securityholders. No representation is
made as to the accuracy of such numbers either as printed on the Securities or
as contained in any notice of redemption and reliance may be placed only on the
other identification numbers placed thereon.

19. GOVERNING LAW
          THIS SECURITY SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY
THE LAWS OF THE STATE OF NEW YORK.

          The Company will furnish to any Securityholder upon written request
and without charge to the Securityholder a copy of the Indenture. Requests may
be made to:

          White Mountains Insurance Group, Ltd.
          80 South Main Street
          Hanover, NH 03755-2053
          Attention: General Counsel

                                      B-10