<PAGE>


                                                                   EXHIBIT 10.26

                                                                  EXECUTION COPY

                            MASTER SERVICES AGREEMENT

            This Agreement, dated as of November 1, 2002, is entered into by and
between The St. Paul Companies, Inc., a Minnesota corporation ("St. Paul"), and
Platinum Underwriters Holdings, Ltd., a Bermuda company ("Platinum").

            WHEREAS, the parties have entered into a Formation and Separation
Agreement (the "Formation and Separation Agreement"), in which they have set
forth certain terms governing St. Paul's sponsorship of the organization of
Platinum and its subsidiaries, actions to be taken in respect of Platinum's
initial public offering (the "Public Offering"), of its common shares, par value
$0.01 per share, and the ongoing relationships between St. Paul and its
subsidiaries and Platinum and its subsidiaries following the consummation of the
Public Offering;

            WHEREAS, as contemplated by the Formation and Separation Agreement,
St. Paul intends to provide, or cause one or more of its Post-closing
Subsidiaries to provide, contingent upon the consummation of the Public
Offering, certain administrative, accounting, human resources, systems and other
support services (together, the "Services") to Platinum or certain of its
Post-closing Subsidiaries, for a specified transition period after the Closing
Date;

            NOW, THEREFORE, in furtherance of the transactions contemplated by
the Formation and Separation Agreement and in consideration of the promises and
the mutual covenants and agreements contained therein and herein and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereby agree as follows:

            1. SERVICES TO BE PROVIDED.

            (a) Services. St. Paul hereby agrees to provide, or cause its
Post-closing Subsidiaries to provide, to Platinum or its Post-closing
Subsidiaries, from and after the Closing Date each of the services (the
"Services") specified on Schedule A hereto (as such may be revised from time to
time pursuant to Section 1(f)).

            (b) Standard for Services. St. Paul shall provide each of the
Services in such manner as Platinum may reasonably request from time to time for
purposes of this Agreement; provided, that St. Paul shall not be required to
provide, or cause to be provided, the Services at a standard materially higher
than the standard generally provided by St. Paul in respect of other business of
St. Paul. St. Paul shall maintain all licenses and authorizations required for
it to provide the Services pursuant to this Agreement.

            (c) Period of Services. St. Paul shall provide each Service until
June 30, 2003 or such shorter period as may be specified in the applicable
Service schedule attached hereto (each such period, the "Maximum Service Period"
for such Service), provided that, for each Service, St. Paul shall in good faith
consider requests by Platinum to extend the time period for provision of the
Service beyond the Maximum Service Period in light of the circumstances at the
time of such request. St. Paul and
<PAGE>

Platinum shall agree upon the terms that will govern the provision of the
particular Service to be so provided at the time that Platinum makes such
request.

            (d) Price of Services. With respect to the provision of each
Service, Platinum shall pay to St. Paul or the St. Paul Subsidiary designated by
St. Paul the "actual cost" to St. Paul or its Subsidiary (which shall consist of
St. Paul's or such Subsidiary's direct and reasonable indirect costs), as the
case may be, as certified in good faith by St. Paul. For greater certainty, the
parties agree that "actual cost" will include any incremental and out-of-pocket
costs incurred by St. Paul in connection with the Services, including the
conversion, acquisition and disposition cost of software and equipment acquired
for the purposes of providing the Services and the cost of establishing
requisite systems and data feeds and hiring necessary personnel.

            (e) Transition Assistance.

                  (i) Exit Strategy. Platinum shall use commercially reasonable
                  efforts in order to terminate the need for the Services as
                  soon as reasonably practicable following the Closing Date (the
                  "Transition"), and in order to accomplish this Transition,
                  Platinum will need assistance from the employees, contractors
                  or managed vendors of St. Paul. St. Paul agrees to assign its
                  Transition coordinator (as set forth in paragraph (ii) below)
                  and to provide other reasonably necessary assistance to allow
                  Platinum and its Post-closing Subsidiaries to exit St. Paul's
                  systems in a timely and efficient manner.

                  (ii) Service Coordinators. Platinum and St. Paul shall each
                  designate one Service coordinator having skills and experience
                  reasonably acceptable to the other party who will provide
                  continuous oversight and coordination of, and communicate
                  concerning disputes with respect to, the Services, who will be
                  available to Platinum and St. Paul during normal business
                  hours and who will be responsible for providing for or
                  delegating the provision of assistance regarding the Services.
                  The Service coordinators will cooperate on a regular basis to
                  plan for the delivery of Services, including the timetable for
                  the provision of such Services and the incurring of related
                  costs. Platinum and St. Paul may from time to time substitute
                  the persons serving as Service Coordinators with other persons
                  qualified to serve in those positions.

                  (iii) Documentation. Subject to any confidentiality or other
                  obligations to third parties, St. Paul will provide to
                  Platinum all


                                      -2-
<PAGE>

                  service operating manuals and other written materials relating
                  to the Services, and any supplements or updates to such
                  manuals and materials, as reasonably requested by Platinum;
                  subject to Section 4, the materials provided pursuant to this
                  clause may be copied by Platinum at its own expense.

            (f) Revisions to Services. This Agreement and the Schedules hereto
are intended to describe all of the Services that Platinum and St. Paul have
determined to be necessary and advisable as of the date hereof, but the parties
anticipate that the complexity of the transactions contemplated by this
Agreement will result in incomplete Schedules. Platinum shall promptly notify
St. Paul in writing if it becomes aware of Services different from or in
addition to those listed on the Schedules hereto that are necessary and
advisable, and the parties will cooperate in good faith to promptly agree to
revisions of the Schedules as necessary and advisable to reflect the intention
of the parties as to the provision of Services and the payment therefor.

            (g) Cooperation. Upon the terms and subject to the conditions and
other agreements set forth herein, each party agrees to use commercially
reasonable efforts to take, or cause to be taken, all actions, and to do, or
cause to be done, and to assist and cooperate with the other party in doing, all
things necessary or advisable to perform the transactions contemplated by this
Agreement.

            2. TERM AND TERMINATION.

            (a) This Agreement shall be construed as a separate and independent
agreement for each Service provided hereunder, provided that this Agreement
shall expire on June 30, 2003, subject to the provisions of Section 1(c). Any
specific Service may be subject to termination at the election of Platinum upon
30 days prior written notice at any time prior to the Maximum Service Period for
such Service, as indicated on the applicable Schedule. Any termination of this
Agreement with respect to any Service shall not terminate the Agreement with
respect to any other Service then being provided subject to this Agreement.
Notwithstanding anything in this Agreement to the contrary, any termination of
this Agreement with respect to any Service shall be final.

            (b) Unless earlier terminated, this Agreement will expire with
respect to each Service provided hereunder at the end of the Maximum Service
Period for such Service.

            (c) Platinum or St. Paul may terminate this Agreement for cause.

            3. BILLING; TAXES. No later than 30 days following the last day of
each calendar quarter, St. Paul shall provide Platinum with a report setting
forth an itemized list of the Services provided to Platinum during such last
calendar quarter, in a


                                      -3-
<PAGE>

form agreed to by the parties. Platinum shall promptly (and in no event later
than 30 days after receipt of such report, unless Platinum is contesting the
amount set forth in the report in good faith) pay to St. Paul by wire transfer
of immediately available funds all amounts payable as set forth in such report.
Each party will pay all taxes for which it is the primary obligor as a result of
the provisions of Services under this Agreement; provided, that Platinum shall
be solely responsible for, and shall reimburse St. Paul in respect of, any
sales, gross receipts or transfer tax payable with respect to the provision of
any Service under this Agreement, and any such reimbursement obligation shall be
in addition to Platinum's obligation to pay for such Service.

            4. RELATIONSHIPS AMONG THE PARTIES, RECIPIENTS AND PROVIDERS.
Nothing in this Agreement shall cause the relationship between St. Paul and
Platinum to be deemed to constitute an agency, partnership or joint venture. The
terms of this Agreement are not intended to constitute any of the parties and
their Affiliates a joint employer for any purpose. Each of the parties agrees
that the provisions of this Agreement as a whole are not intended to, and do
not, constitute control of the other party (or any Affiliates thereof) or
provide it with the ability to control such other party (or any Affiliates
thereof), and each party hereto expressly disclaims any right or power under
this Agreement to exercise any power whatsoever over the management or policies
of the other (or any Affiliates thereof). Nothing in this Agreement shall oblige
either party hereto to act in breach of the requirements of any law, rule or
regulation applicable to it, including securities and insurance laws, written
policy statements of securities commissions, insurance and other regulatory
authorities, and the by-laws, rules, regulations and written policy statements
of relevant securities and self-regulatory organizations.

            5. REQUIREMENTS. Nothing in this Agreement requires Platinum or any
of its Post-closing Subsidiaries to purchase any particular quantity or level of
any Service provided under this Agreement.

            6. REGULATORY MATTERS. St. Paul will cooperate, and will cause any
of its Post-closing Subsidiaries providing Services hereunder to cooperate, with
each of Platinum and its Post-closing Subsidiaries and any regulatory
authorities to satisfy any regulatory requirements applicable to entities that
provide services to Platinum or its Post-closing Subsidiaries.

            7. GOVERNING LAW. This agreement shall be governed by, and construed
in accordance with, the laws of the State of New York, without regard to its
conflict of laws principles.

            8. DISPUTE RESOLUTION.


                                      -4-
<PAGE>

            (a) Mandatory Arbitration. The parties hereto shall promptly submit
any dispute, claim, or controversy arising out of or relating to this Agreement
and/or the provision of Services hereunder, including effect, validity, breach,
interpretation, performance, or enforcement (collectively, a "Dispute") to
binding arbitration in New York, New York at the offices of Judicial Arbitration
and Mediation Services, Inc. ("JAMS") before an arbitrator (the "Arbitrator") in
accordance with JAMS' Comprehensive Arbitration Rules and Procedures and the
Federal Arbitration Act, 9 U.S.C. Sections 1 et seq. The Arbitrator shall be a
former judge selected from JAMS' pool of neutrals. The parties agree that,
except as otherwise provided herein respecting temporary or preliminary
injunctive relief, binding arbitration shall be the sole means of resolving any
Dispute. Judgment on any award of the Arbitrators may be entered by any court of
competent jurisdiction.

            (b) Costs. The costs of the arbitration proceeding and any
proceeding in court to confirm or to vacate any arbitration award or to obtain
temporary or preliminary injunctive relief as provided in paragraph (c) below,
as applicable (including, without limitation, actual attorneys' fees and costs),
shall be borne by the unsuccessful party and shall be awarded as part of the
Arbitrator's decision, unless the Arbitrator shall otherwise allocate such costs
in such decision.

            (c) Injunctive Relief. The parties hereto may seek or obtain
temporary or preliminary injunctive relief in a court for any breach or
threatened breach of any provision hereof pending the hearing before and
determination of the Arbitrator. St. Paul hereby agrees that it shall continue
to provide, or cause its Affiliates to provide, any and all Services pending the
hearing before and determination of the Arbitrator, it being agreed and
understood that the failure to so provide may cause irreparable harm to Platinum
and its Affiliates and that the putative breaching party has assumed all of the
commercial risks associated with such breach or threatened breach of any
provision hereof by such party.

            (d) Courts. The parties agree that the State and Federal courts in
The City of New York shall have jurisdiction for purposes of enforcement of
their agreement to submit Disputes to arbitration and of any award of the
Arbitrator.

            9. ASSIGNMENT. Neither this Agreement nor the rights or obligations
hereunder shall be assignable by either party hereto, by operation of law or
otherwise, without the prior written consent of the other party hereto, and any
purported assignment shall be null and void. Subject to the foregoing, this
Agreement shall inure to the benefit of and be binding upon the parties hereto
and their respective successors and assigns.

            10. FORCE MAJEURE/DELAY. No party will be responsible if it is
prevented from complying, either totally or in part, with any of the terms or
provisions of this Agreement by reason of an Event of Force Majeure (as defined
below), and such


                                      -5-
<PAGE>

party shall have no liability to the other party in connection therewith;
provided, that such party shall have a duty reasonably to mitigate, or cause to
be mitigated, any such failure to comply. As used in the Agreement, an "Event of
Force Majeure" means any of the following: fires, floods, earthquakes, elements
of nature or acts of God; acts of war, terrorism, riots, civil disorders,
rebellions or revolutions; strikes, lockouts or labor difficulties; power
outages, equipment failures, computer viruses or malicious acts of third
parties; and laws, orders, proclamations, regulations, ordinances, demands or
requirements of governmental authorities.

            11. INDEMNIFICATION.

            (a) Platinum shall indemnify and hold harmless, to the full extent
permitted by law, St. Paul, its Post-closing Subsidiaries and their respective
officers, directors and employees ("St. Paul Indemnitees") from and against any
and all Losses of any of the St. Paul Indemnitees arising out of or based upon
any actions taken or refrained from being taken by any such St. Paul Indemnitee
at the direction of Platinum pursuant to this Agreement, or any breach by
Platinum of any of its covenants under this Agreement.

            (b) St. Paul shall indemnify and hold harmless, to the full extent
permitted by law, Platinum, its Post-closing Subsidiaries and their respective
officers, directors and employees ("Platinum Indemnitees") from and against any
and all Losses of any of the Platinum Indemnitees arising out of or based upon
the negligence or willful misconduct of any Person providing Services, or any
breach by St. Paul of any of its covenants under this Agreement. Notwithstanding
anything to the contrary in this Agreement, the maximum amount of indemnifiable
losses which may be recovered from St. Paul shall under no circumstances exceed
the aggregate fees paid to St. Paul by Platinum pursuant to Section 1(d).

            (c) Except with respect to claims relating to actual fraud, the
indemnification provisions set forth in this section are the sole and exclusive
remedy of the parties hereto for any and all claims for indemnification under
this Agreement.

            12. ADDITIONAL SERVICES. To the extent that, at the request of
Platinum or as required under the terms of this Agreement, St. Paul or any of
its Affiliates provides services to, or performs activities for the benefit of,
Platinum or any of its Affiliates in addition to the Services, including without
limitation pursuant to Sections 1(f) and 6 hereof, Platinum shall promptly
reimburse St. Paul for the actual cost to St. Paul or such Affiliate, as the
case may be, of providing such services or performing such activities.

            13. ENTIRE AGREEMENT. This Agreement and the Formation and
Separation Agreement constitute the entire agreement, and supersede all prior
agreements


                                      -6-
<PAGE>

and understandings (oral and written), by and among the parties hereto with
respect to the subject matter hereof.

            14. NO THIRD-PARTY RIGHTS. Nothing contained in this Agreement,
express or implied, establishes or creates, or is intended or will be construed
to establish or create, any right in or remedy of, or any duty or obligation to,
any third party other than Platinum's Subsidiaries.

            15. NOTICES. All notices, requests, claims, demands and other
communications hereunder shall be in writing and shall be deemed to have been
duly given if delivered by hand (with receipt confirmed), or by certified mail,
postage prepaid and return receipt requested, or by facsimile addressed as
follows (or to such other address as a party may designate by written notice to
the others) and shall be deemed given on the date on which such notice is
received:

                  If to St. Paul:

                  The St. Paul Companies, Inc.
                  385 Washington Street
                  St. Paul, Minnesota 55102
                  Attn.: General Counsel
                  Facsimile:  (410) 205-6967

            With a copy to:

                  Donald R. Crawshaw
                  Sullivan & Cromwell
                  125 Broad Street
                  New York, New York  10004
                  Facsimile:  (212) 558-3588

            If to Platinum:

                  Platinum Underwriters Holdings, Ltd.
                  Clarendon House
                  2 Church Street
                  Hamilton HM 11
                  Bermuda
                  Attn.:   Secretary
                  Facsimile:  (441) 292-4720

            With a copy to:


                                      -7-
<PAGE>

                  Linda E. Ransom
                  Dewey Ballantine LLP
                  1301 Avenue of the Americas
                  New York, New York 10019
                  Facsimile:  (212) 259-6576

            16. COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which shall
constitute one and the same instrument.

            17. AMENDMENT; MODIFICATION. The parties may by written agreement,
subject to any regulatory approval as may be required, (a) extend the time for
the performance of any of the obligations or other acts of the parties hereto;
(b) waive any inaccuracies in the documents delivered pursuant to this
Agreement, and (c) waive compliance with or modify, amend or supplement any of
the agreements contained in this Agreement or waive or modify performance of any
of the obligations of any of the parties hereto. This Agreement may not be
amended or modified except by an instrument in writing duly signed on behalf of
the parties hereto.

            18. WAIVER. No failure by any party to take any action or assert any
right hereunder shall be deemed to be a waiver of such right in the event of the
continuation or repetition of the circumstances giving rise to such right,
unless expressly waived in writing.

            19. SEVERABILITY. To the extent any provision of this Agreement
shall be invalid or unenforceable, it shall be considered deleted herefrom and
the remaining provisions of this Agreement shall be unaffected and shall
continue in full force and effect.

            20. SPECIFIC PERFORMANCE AND OTHER EQUITABLE RIGHTS. Each of the
parties recognizes and acknowledges that neither St. Paul nor Platinum would
contemplate the provision of Services hereunder unless this Agreement was
executed and that a breach by a party of any covenants or other commitments
contained in this Agreement will cause the other party to sustain injury for
which it would not have an adequate remedy at law for money damages. Therefore,
each of the parties agrees that in the event of any such breach, the aggrieved
party shall be entitled to the remedy of specific performance of such covenants
or commitments and preliminary and permanent injunctive and other equitable
relief in addition to any other remedy to which it may be entitled, at law or in
equity, and the parties further agree to waive any requirement for the securing
or posting of any bond in connection with the obtaining of any such injunctive
or other equitable relief.


                                      -8-
<PAGE>

            21. RETENTION OF RECORDS. This Agreement will be retained as part of
the official records of Platinum and St. Paul for the term of the Agreement and
five years thereafter.

            22. HEADINGS. Headings contained in this Agreement are for reference
purposes only and shall not affect in any way the meaning or interpretation of
this Agreement.

            23. DEFINITIONS; FORMATION AND SEPARATION AGREEMENT. Capitalized
terms used but not defined in this Agreement have the meanings specified in the
Formation and Separation Agreement.

            24. EFFECTIVENESS. This Agreement shall become effective contingent
upon the consummation of the Public Offering, without any further action by
either of the parties hereto.


                                      -9-
<PAGE>

            IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed and delivered by their duly authorized officers as of the date first
above written.

                                     THE ST. PAUL COMPANIES, INC.

                                     By: /s/ Bruce A. Backberg
                                         --------------------------------
                                         Name: Bruce A. Backberg
                                         Title: Senior Vice President and
                                                Corporate Secretary


                                     PLATINUM UNDERWRITERS HOLDINGS, LTD.

                                     By: /s/ Jerome T. Fadden
                                         --------------------------------
                                         Name: Jerome T. Fadden
                                         Title: President and
                                                Chief Executive Officer
<PAGE>

SCHEDULE A

1.    Claim processing and payment for all business written on St. Paul paper
      and subject to the Quota Share Retrocession Agreements (as such term is
      defined in the Formation and Separation Agreement).

2.    Billing and collection services for balances due to/from from brokers and
      cedents for all business written on St. Paul paper and subject to the
      Quota Share Retrocession Agreements.

3.    Processing, billing and collection services for all retrocessional premium
      and loss inuring to the benefit of Platinum for all business written on
      St. Paul paper subject to the Quota Share Retrocession Agreements.

4.    Processing and accounting services, as may be required by Platinum, for
      payroll and benefits.

5.    Provision of historical underwriting data with respect to the experience
      of the St. Paul Re division of St. Paul in format to be prescribed by
      Platinum.

6.    Provision of ongoing underwriting data with respect to the business ceded
      to Platinum under the Quota Share Retrocession Agreements.


                                      -11-
<PAGE>

                       MASTER SERVICE AGREEMENT-SCHEDULE A

<TABLE>
<CAPTION>
   DESCRIPTION OF        DESCRIPTION OF     LEVEL OF     QUALITY OF     MAXIMUM          PRICE OF     CONTACT PERSON   ISSUES
  RESPONSIBILITIES       FACILITIES AND     SERVICE      SERVICE        SERVICE          SERVICES
                         ASSETS TO BE                                   PERIOD FROM
                         USED IN                                        CLOSING
                         PROVIDING
                         SERVICES
<S>                      <C>                <C>          <C>            <C>             <C>           <C>              <C>
                                                          FINANCE

1.   St. Paul Re will    St. Paul Re                                     Ongoing        Actual Cost   IS contact
     provide access      personnel to                                                                 Ni Qin-Feng
     to or the actual    provide
     reserving           information to
     triangles at a      Platinum in St.
     reserving class     Paul Re's data
     level.              elements and
                         formats

2.   Provide                                                             Ongoing        Actual        Claude
     accounting                                                          until          Cost based    Chevance
     guidance for Non                                                    Platinum       on an
     traditional                                                         ceases to      hourly
     accounts before                                                     write Non      rate.
     a commitment is                                                     traditional
     made by                                                             business on
     Platinum's                                                          St. Paul's
     underwriting to                                                     paper or 6
     write the                                                           months on
     business.                                                           Platinum's
                                                                         paper.

                                                      HUMAN RESOURCES

1.   Administrative      Payroll,                                        Ongoing        $146 per
     charges are         Benefits and HR                                                employee
     utilized within     Support                                                        per month
     The St. Paul
     Companies, Inc.
     to account for
     internally
     sourced services
     and represent
     the aggregate
     cost of HR
     services
     provided on a
     per employee
     basis.

2.   The St. Paul                                                        Ongoing      $30,000
     Companies, Inc.                                                                  one time
     is required to                                                                   payment
     purchase an
     additional
     license from
     PeopleSoft to
     administer
     payroll and
     benefits for
     Platinum.
</TABLE>

<PAGE>

                       MASTER SERVICE AGREEMENT-SCHEDULE A

<TABLE>
<CAPTION>
   DESCRIPTION OF        DESCRIPTION OF     LEVEL OF     QUALITY OF     MAXIMUM          PRICE OF     CONTACT PERSON   ISSUES
  RESPONSIBILITIES       FACILITIES AND     SERVICE      SERVICE        SERVICE          SERVICES
                         ASSETS TO BE                                   PERIOD FROM
                         USED IN                                        CLOSING
                         PROVIDING
                         SERVICES
<S>                      <C>                <C>          <C>            <C>             <C>           <C>              <C>

                                                      INFORMATION SYSTEMS

1.  Provide help                                                        4 months, or    Actual cost   Eddie Morales
    desk/hands-on                                                       until either                  (Operator)
    technical support                                                   party stops
    for "First Shift"                                                   occupying
    computer room                                                       the premises
    operations                                                          at 195
                                                                        Broadway,
                                                                        New York, NY
                                                                        (the
                                                                        "Premises"),
                                                                        which ever
                                                                        is earlier.

2.  Provide help                                                        December 31     Actual cost   Chung Wong
    desk/hands-on                                                       2002
    technical support
    for C Programming
</TABLE>