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                                                                  EXHIBIT 10.21

                                                                  EXECUTION COPY

                         REGISTRATION RIGHTS AGREEMENT

      REGISTRATION RIGHTS AGREEMENT (this "Agreement"), dated as of November 1,
2002, between THE ST. PAUL COMPANIES, INC., a company incorporated under the
laws of Minnesota ("St. Paul") and PLATINUM UNDERWRITERS HOLDINGS, LTD., a
company incorporated under the laws of Bermuda (the "Company").

                                    RECITALS

      WHEREAS, St. Paul and the Company are parties to the Formation and
Separation Agreement dated as of October 28, 2002, and the Option Agreement,
dated as of November 1, 2002 (respectively, the "Formation and Separation
Agreement" and the "Option Agreement"), each relating to the purchase by St.
Paul of common shares, par value U.S. $0.01 per share (the "Common Shares"), of
the Company;

      WHEREAS, the Company will effect an initial public offering of certain
Common Shares pursuant to a Registration Statement on Form S-1 (File No.
333-86906) (the "Public Offering"); and

      WHEREAS, the Company has agreed to provide the registration rights
specified in this Agreement to St. Paul following the Public Offering and the
Company and St. Paul are entering into this Agreement to set forth the terms and
conditions applicable to the grant and exercise of such registration rights.

      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 is hereby
acknowledged by the parties hereto, the Company and St. Paul hereby agree as
follows:

                                    ARTICLE I

                                   DEFINITIONS

      1.1. DEFINED TERMS. As used in this Agreement, the following capitalized
terms have the respective meanings set forth below:

      "Affiliate" means, with respect to any person, any other person that
directly or indirectly through one or more intermediaries controls or is
controlled by or is under common control with such person.

      "Bye-laws" means the Bye-laws of the Company, as the same may be further
amended from time to time.

      "Capital Securities" means all shares of each class in the capital stock
of the Company and all securities convertible into or exchangeable or
exercisable for any such shares.

      "Closing" means the closing of the Public Offering pursuant to an
effective registration statement under the Securities Act.

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      "Closing Price" for each day is the reported last sale price regular way
or, in case no such reported sale takes place on such day, the average of the
reported closing bid and asked prices regular way, in either case on the New
York Stock Exchange or, if the Common Shares are not listed or admitted to
trading on such Exchange, on the principal national securities exchange on which
the Common Shares are listed or admitted to trading or, if not listed or
admitted to trading on any national securities exchange, on the NASDAQ National
Market or, if the Common Shares are not listed or admitted to trading on any
national securities exchange or quoted on the NASDAQ National Market, the
average of the closing bid and asked prices in the over-the-counter market as
furnished by any New York Stock Exchange member firm reasonably selected from
time to time by the Board of Directors of the Company for that purpose.

      "Common Shares" has the meaning specified in the Recitals.

      "Current Market Price" means the average of the daily Closing Prices per
share for the ten consecutive Trading Days ending on the day before the
applicable record date.

      "Exchange Act" means the U.S. Securities Exchange Act of 1934, as amended.

      "Formation and Separation Agreement" has the meaning specified in the
Recitals.

      "Option Agreement" has the meaning set forth in the Recitals.

      "person" means any individual, corporation, company, partnership, joint
venture, trust, association, government or governmental body or other entity.

      "Public Offering" has the meaning specified in the Recitals.

      "Registrable Shares" means, at any time, any and all Common Shares owned
by the St. Paul Group, whether purchased by St. Paul as contemplated by the
Formation and Separation Agreement, issued to St. Paul pursuant to the Option
Agreement or otherwise acquired, as the case may be, other than shares that have
ceased to be Registrable Shares. Common Shares cease to be Registrable Shares
(a) when a registration statement with respect to the disposition of such shares
has become effective under the Securities Act and such shares shall have been
disposed of pursuant to such registration statement, or (b) when such shares
have been sold pursuant to Rule 144 under the Securities Act.

      "Registration Expenses" means any and all expenses incident to performance
of or compliance with the demand rights set forth in Section 2.1 and piggy-back
rights set forth in Section 2.2, including, (a) all SEC and stock exchange or
National Association of Securities Dealers, Inc. registration and filing fees,
(b) all fees and expenses of complying with state securities or blue sky laws
(including reasonable fees and disbursements of counsel for the underwriters in
connection with blue sky qualifications of the Registrable Shares), (c) the cost
of printing or preparing any registration statement, prospectus, offering
circular, agreement among underwriters, underwriting agreement, blue sky
memorandum, share certificates and any other documents in connection with the
offering, purchase, sale and delivery of the Registrable Shares, (d) the costs
and charges of any transfer agent and registrar and any custodian or
attorney-in-fact appointed to act on behalf of St. Paul, (e) all messenger and
delivery expenses of the Company, (f) the reasonable fees and expenses of any
qualified independent underwriter, (g) the reasonable fees and disbursements of
counsel for the Company and the Company's independent public accountants,
including the expenses of any special


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audits and/or "cold comfort" letters required by or incident to such performance
and compliance and (h) any road show and marketing expenses; provided that St.
Paul shall pay the fees and disbursements of its own counsel, if any, and all
underwriting discounts, commissions and transfer taxes, if any, relating to the
sale or disposition of its Registrable Shares.

      "Rule 144" means Rule 144 under the Securities Act.

      "St. Paul Group" means St. Paul and its Affiliates at such time.

      "St. Paul Option" means the option of St. Paul to purchase additional
Common Shares pursuant to the Option Agreement.

      "Securities Act" means the U.S. Securities Act of 1933, as amended.

      "SEC" means the U.S. Securities and Exchange Commission or any other U.S.
federal agency at the time administering the Securities Act or the Exchange Act.

      "shareholder" means, with respect to any Common Shares, the person in
whose name such shares are registered in the register of members maintained by
the Company in accordance with applicable law and the Bye-laws, and the terms
"hold," "held" and "holding" shall have meanings correlative to the foregoing.

      "10% Shareholder" has the meaning set forth in the Bye-laws.

      "Termination Date" means the first date after the Closing on which St.
Paul does not have right to make a Demand Request.

      "Trading Day" means each Monday, Tuesday, Wednesday, Thursday and Friday,
other than any day on which the Common Shares are not traded on the applicable
securities exchange or on the applicable securities market.

      "United States 25% Shareholder" has the meaning set forth in the Bye-laws.

      1.2. GENERAL. (a) Unless the context otherwise requires, references in
this Agreement to any "section" or "article" mean a section or article of this
Agreement, as the case may be, and the terms "hereof," "hereunder," "hereto" and
words of similar meaning mean this Agreement in its entirety and not any
particular provisions of this Agreement. Unless the context otherwise requires,
the terms defined herein include the singular as well as the plural.

      (b) Unless the context otherwise requires, each reference herein to the
Securities Act, the Exchange Act or Rule 144 (or any other rule, regulation or
form promulgated under either such statute) shall be deemed to mean, as of any
time, such statute, rule, regulation or form as then in effect, after all
amendments thereto, or, if not then in effect, any successor statute, rule,
regulation or form as then in effect, after all amendments thereto.


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                                   ARTICLE II

                               REGISTRATION RIGHTS

      2.1. DEMAND RIGHTS. (a) From and after the first anniversary of the
Closing (unless the Company consents to an earlier date, such consent not to be
unreasonably withheld), St. Paul has the right, on four occasions, to require
the Company to file a registration statement on Form S-1, S-2 or S-3 (or Form
F-1, F-2 or F-3) or any similar or successor to such Forms under the Securities
Act for a public offering of Registrable Shares, by delivering to the Company
written notice, with a copy to RenaissanceRe Holdings Ltd., stating that such
right is being exercised, naming, if applicable, the members of the St. Paul
Group whose Registrable Shares are to be included in such registration
(collectively, the "Demanding Shareholders"), specifying the number of each such
Demanding Shareholder's Registrable Shares to be included in such registration
and describing the intended method of distribution thereof (a "Demand Request");
provided that St. Paul shall not make a Demand Request during the 180-day period
immediately following the Closing except with the prior written consent of
Goldman, Sachs & Co., Merrill Lynch, Pierce, Fenner & Smith Incorporated and
Salomon Smith Barney Inc.; and provided further, that, from and after the fifth
anniversary of the Closing, St. Paul has the right to two additional Demand
Requests if on such date St. Paul is the beneficial owner (directly or
indirectly) of more than 9.9% of the Common Shares then outstanding. Upon
receipt of a Demand Request, the Company shall use its reasonable best efforts
to promptly effect the registration under the Securities Act of the Registrable
Shares included in the Demand Request to permit the Demanding Shareholders to
sell or otherwise dispose of their respective Registrable Shares included in the
registration in accordance with the method or methods of distribution intended
by the Demanding Shareholders. The rights and obligations of the parties listed
under this Section 2.1(a) are subject to the other provisions of this Agreement.

      (b) The Company's obligations pursuant to Section 2.1(a) above are subject
to the following conditions:

            (i) the Company is not obligated to fulfill a Demand Request if it
      has fulfilled a Demand Request received during the period of 12 months
      immediately preceding the date of receipt of such Demand Request;

            (ii) the Company is not obligated to fulfill a Demand Request unless
      the Demand Request is for such number of Registrable Shares with a market
      value that is equal to at least $50 million as of the date of such Demand
      Request, provided that the last Demand Request (as specified in Section
      2.1(a) of this Agreement) will not be subject to the limitations of this
      Section 2.01(b)(ii); and

            (iii) the Company shall, if requested by St. Paul, undertake a "road
      show" and other customary marketing efforts in connection with the sale of
      Registrable Shares pursuant to such registration, at such times and in
      such manner as St. Paul may reasonably request.

            (iv) the Company is not obligated to fulfill the requirements herein
      with regard to any registration relating to a Demand Request:

                  (A) during any period of time (not to exceed ninety (90) days
            in the aggregate during any period of twelve (12) consecutive
            months) after the Company has determined to proceed with a
            Securities Act registration of any of its securities and is
            diligently proceeding


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            to complete such registration or any offering of securities pursuant
            thereto (whether for its own account or that of any shareholder but
            excluding any registration on Form S-8 under the Securities Act or
            any similar or successor form) if, in the judgment of a nationally
            recognized investment banking firm (which may be acting as managing
            underwriter for any such offering or as financial advisor to the
            Company), the fulfillment of such requirements or such filing would
            have an adverse effect on the offering,

                  (B) during any period of time (not to exceed ninety (90) days
            during any period of twelve (12) consecutive months) when the
            Company is in possession of material, non-public information that
            the Company would not be required to disclose publicly in the
            absence of any Securities Act registration of its securities, and
            the disclosure of which would be materially injurious to the
            Company, or

                  (C) during any period of time (not to exceed ninety (90) days
            during any period of twelve (12) consecutive months) when the
            Company is engaged in, or has determined to engage in and is
            proceeding diligently with, any program for the purchase of, or any
            tender offer or exchange offer for, its Capital Securities, and
            determines, on advice of nationally recognized independent U.S.
            counsel knowledgeable in such matters, that such program or offer
            and the requested registration may not proceed concurrently without
            violating Regulation M under the Exchange Act.

            (v) the Company is not required to maintain the effectiveness of a
      registration statement filed pursuant to Section 2.1(a) for a period in
      excess of 90 consecutive days, which period shall be tolled during any
      period in which the Company invokes its rights under Section 2.6;
      provided, however, that, from and after the third anniversary of the
      Closing and receipt thereafter by the Company of written instructions from
      St. Paul to such effect, in the case of any registration of Registrable
      Shares on Form S-3 or F-3 which are intended to be offered on a continuous
      or delayed basis, such 90-day period shall be extended until all such
      Registrable Shares are sold, provided that Rule 415, or any successor rule
      under the Securities Act, permits an offering on a continuous or delayed
      basis, provided further that applicable rules under the Securities Act
      governing the obligation to file a post-effective amendment permit, in
      lieu of filing a post-effective amendment which (1) includes any
      prospectus required by Section 10(a) of the Securities Act or (2) reflects
      facts or events representing a material or fundamental change in the
      information set forth in the registration statement, the incorporation by
      reference of information required to be included in (1) and (2) above to
      be contained in periodic reports filed pursuant to Section 13 or 15(d) of
      the Exchange Act in the registration statement and provided further that
      St. Paul shall give the Company written notice, with a copy to
      RenaissanceRe Holdings Ltd., at least ten business days prior to the
      beginning of any fiscal quarter in which St. Paul intends to attempt to
      sell, transfer or otherwise distribute any Common Shares pursuant to this
      subsection (v) which are offered on a continuous or delayed basis, which
      notice shall specify the aggregate number of Common Shares St. Paul
      intends to attempt to sell, transfer or dispose of in such fiscal quarter;

            (vi) the Company shall not be required to file or maintain any
      registration statement that permits a delayed or continuous offering to be
      made for more than 30 consecutive days, which period shall be tolled
      during any period in which the Company invokes its rights under Section
      2.6, after such registration statement becomes effective;


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            (vii) any underwriting agreement entered into in connection with any
      public offering pursuant to this Article II shall contain a provision
      pursuant to which the managing underwriter of any such public offering
      shall agree to use its reasonable best efforts to avoid selling
      Registrable Shares to any one person or group of related persons (other
      than another dealer acting as an underwriter or member of any selling
      group in connection with such public offering) if, as a result of such
      sale, any such person would own directly or indirectly through a foreign
      corporation, or constructively under applicable rules contained in the
      Internal Revenue Code of 1986, as amended, more than 9.9% of the Common
      Shares; and

            (viii) St. Paul is entitled to designate any one or more lawful
      methods of distribution permitted pursuant to the registration statement
      (including a firm commitment underwriting) to be the method of
      distribution for the registration pursuant to this Section 2.1, and St.
      Paul will sell its Registrable Shares included in the registration in the
      designated methods (and, in the case of any underwriting, on the same
      terms and conditions as the Company and any other selling shareholder);
      the intended methods of distribution shall be indicated in the Demand
      Request and shall be finally determined prior to filing the registration
      statement. In any distribution pursuant to a Demand Request involving an
      underwriter, St. Paul is entitled to select any nationally recognized
      investment banking firm to act as underwriter, provided that with respect
      to any Demand Requests and piggy- back registrations for which the Company
      bears the costs and expenses pursuant to Section 2.7, such selection of an
      underwriter by St. Paul is subject to the consent of the Company, such
      consent not to be unreasonably withheld.

      (c) Subject to Section 2.3, the Company may elect to include in any
registration statement filed pursuant to this Section 2.1 any Common Shares to
be issued by it or held by any of its subsidiaries or by any other shareholders
only to the extent such shares are offered and sold pursuant to, and on the
terms and subject to the conditions of, any underwriting agreement or
distribution arrangements entered into or effected by the Demanding
Shareholders.

      (d) St. Paul may withdraw a Demand Request at any time. A Demand Request
withdrawn pursuant to this Section 2.1(d) is deemed not to have been made for
purposes of Section 2.1 and is of no further effect if and only if St. Paul pays
or reimburses the Company for all expenses and costs incurred by the Company in
connection with such Demand Request.

      2.2. "PIGGY-BACK" RIGHTS. If at any time after the Closing the Company
proposes to register, for its own account or for the account of any shareholder,
any Common Shares on a registration statement on Form S-1, S-2 or S-3 (or Form
F-1, F-2 or F-3) or any similar or successor to such Forms under the Securities
Act for purposes of a public offering of such Common Shares, other than pursuant
to a Demand Request, St. Paul has the right to include any Registrable Shares in
such registration. The Company shall give prompt written notice of any such
proposal, including the intended method of distribution of such Common Shares,
to St. Paul. Subject to Section 2.3, upon the written request (a "Piggy-Back
Request") of St. Paul, given within fifteen (15) business days after the
transmittal of any such written notice, the Company will use its reasonable best
efforts to include in such public offering any or all of the Registrable Shares
then held by St. Paul, or, if applicable, the St. Paul Group, to permit the sale
of such Registrable Shares pursuant to the intended method or methods of
distribution; provided that any participation in such public offering by St.
Paul must be on substantially the same terms as the Company's and each other
shareholder's participation therein; and provided further, that the total number
of Common Shares to be included in any such public offering may not exceed the
Maximum Number (as defined below), and Common Shares must be allocated


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to give effect to this proviso as provided in Section 2.3. St. Paul has the
right to withdraw a Piggy-Back Request by giving written notice to the Company
of its election to withdraw such request at least five (5) business days prior
to the proposed filing date of such registration statement. Each Piggy-Back
Request by St. Paul must specify the members of the St. Paul Group whose
Registrable Shares are to be included in the registration and the number of such
shares for each such member. The Company is entitled to select any nationally
recognized investment banking firm as underwriter in a registration pursuant to
this Section 2.2.

      2.3. ALLOCATION OF SECURITIES INCLUDED IN A PUBLIC OFFERING. If the
managing underwriter or placement agent for any public offering effected
pursuant to Section 2.1 or Section 2.2 (or, if there is none, a nationally
recognized investment banking firm acting as financial advisor to the Company)
advises the Company and St. Paul in writing that the number of Common Shares
sought to be included in such public offering (including those sought to be
offered by the Company and those sought to be offered by St. Paul) exceeds the
maximum number of Common Shares whose inclusion in such public offering would
not be reasonably likely to have an adverse effect on the price, timing or
distribution of the Common Shares included in such public offering (the "Maximum
Number"), the Company shall allocate Common Shares to be included in such public
offering up to the Maximum Number as follows:

      (a)   in the case of any registration pursuant to Section 2.1, first to
            the Demanding Shareholders, subject, if applicable, to allocation
            below the Maximum Number in such manner as they may agree among
            themselves; then, as to any excess, to the Company; and

      (b)   in the case of any registration pursuant to Section 2.2, first to
            the Company for its own account; then to St. Paul and each other
            shareholder designated by the Company, subject to allocation below
            the Maximum Number pro rata according to the number of Registrable
            Shares held by the St. Paul Group or by such other shareholder, as
            the case may be.

St. Paul may allocate any allocation made to it pursuant to this Section 2.3
among the members of the St. Paul Group as it wishes. The Company may allocate
any allocation made to it pursuant to Section 2.3(a) among itself, its
subsidiaries and its shareholders as it wishes, and may allocate any allocation
made to it for its own account pursuant to Section 2.3(b) among itself and its
subsidiaries as it wishes.

      2.4. INDEMNIFICATION. (a) The Company shall indemnify, to the extent
permitted by law, and hold harmless St. Paul and each member of the St. Paul
Group and each underwriter against any losses, claims, damages or liabilities,
joint or several, or actions in respect thereof ("Claims"), to which such
indemnified party may become subject, under the Securities Act of 1933
("Securities Act") or otherwise, insofar as such Claims arise out of or are
based upon any untrue statement or alleged untrue statement of any material fact
contained in the registration statement, in any prospectus or preliminary
prospectus included in such registration statement or in any amendment or
supplement thereto filed with the SEC (collectively, "Registration Documents")
or insofar as such Claims arise out of or are based upon the omission or alleged
omission to state in any Registration Document a material fact required to be
stated therein or necessary to make the statements made therein not misleading,
and will reimburse any such indemnified party for any legal or other expenses
reasonably incurred by such indemnified party in investigating or defending any
such Claim as such expenses are incurred; provided that the Company is not
liable in any such case to the extent that any such Claim arises out of or is
based upon an untrue statement or alleged untrue statement or omission or
alleged omission made in any Registration Document in reliance upon and in
conformity with written information furnished to the Company by or on behalf of
such indemnified party specifically for use in the preparation of such
Registration Document and provided further that the Company is not liable to


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indemnify St. Paul or any member of the St. Paul Group to the extent that any
such claim arises out of or is based upon an untrue statement or alleged untrue
statement or omission or alleged omission made in any Registration Document in
the historical financial statements of the Reinsurance Division of St. Paul or
financial information in any Registration Document derived therefrom.

      (b) In connection with any registration in which St. Paul is
participating, St. Paul shall indemnify, to the extent permitted by law, and
hold harmless the Company and each underwriter against any Claims to which each
such indemnified party may become subject under the Securities Act or otherwise,
insofar as such Claims arise out of or are based upon any untrue statement or
alleged untrue statement of any material fact contained in any Registration
Document, or insofar as any claims arise out of or are based upon the omission
or alleged omission to state in any Registration Document a material fact
required to be stated therein or necessary to make the statements made therein
not misleading; provided, however, that such indemnification is payable only if,
and to the extent that, any such Claim arises out of or is based upon an untrue
statement or alleged untrue statement or omission or alleged omission made in
any Registration Document in reliance upon and in conformity with written
information furnished to the Company by or on behalf of St. Paul or any member
of the St. Paul Group specifically for use in the preparation of such
Registration Document.

      (c) Any person entitled to indemnification under Section 2.4(a) or (b)
above shall notify promptly the indemnifying party in writing of the
commencement of any Claim if a claim for indemnification in respect thereof is
to be made against an indemnifying party under this Section 2.4, but the
omission of such notice shall not relieve the indemnifying party from any
liability which it may have to any indemnified party otherwise than under
Section 2.4(a) or (b). In case any action is brought against an indemnified
party and it shall notify the indemnifying party of the commencement thereof,
the indemnifying party is entitled to participate in, and, to the extent that it
chooses, to assume the defense thereof with counsel reasonably acceptable to the
indemnified party, who may be counsel for the indemnifying party unless the
indemnified party reasonably concludes such counsel would have a conflict of
interest in representing both indemnified and indemnifying parties (provided
that the Company is not responsible for the fees and expenses of more than one
counsel for all indemnified parties with respect to any Claim or group of Claims
alleged to have arisen from similar facts); and, after notice from the
indemnifying party to the indemnified party that it so chooses, the indemnifying
party is not liable for any legal or other expenses subsequently incurred by the
indemnified party in connection with the defense thereof other than reasonable
costs of investigation. The indemnifying party is not liable for any settlement
of any proceeding effected without its written consent, but if settled with such
consent or if there be a final judgment for the plaintiff, the indemnifying
party agrees to indemnify the indemnified party from and against any loss or
liability by reason of such settlement or judgment. No indemnifying party may,
without the prior written consent of the indemnified party, effect any
settlement of any pending or threatened proceeding in respect of which any
indemnified party is or could have been a party and indemnity could have been
sought hereunder by such indemnified party, unless such settlement includes an
unconditional release of such indemnified party from all liability on claims
that are the subject matter of such proceeding.

      (d) If for any reason the foregoing indemnity is unavailable to, or is
insufficient to hold harmless, an indemnified party in respect of any Claim, (i)
if the indemnified party is an underwriter, then each indemnifying party shall
contribute to the amount paid or payable by the indemnified party as a result of
any Claim in such proportion as is appropriate to reflect the relative benefits
received by St. Paul and the Company, on the one hand, and the indemnified
party, on the other, from the offering of securities to which such Registration
Documents relate, (ii) as between the Company and St. Paul, the indemnifying
party shall contribute to the amount paid or payable by the indemnified party as
a result of any Claim in such proportion


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as is appropriate to reflect the relative benefits to and the relative fault of
the indemnifying party, on the one hand, and the indemnified party, on the
other, in connection with the statements or omissions that resulted in such
Claims, as well as any other relevant equitable considerations. If, however, the
allocation provided in clause (i) or (ii) of the immediately preceding sentence
is not permitted by applicable law, or if the indemnified party failed to give
the notice required by clause (c) above, then each indemnifying party shall
contribute to the amount paid or payable by such indemnified party in such
proportion as is appropriate to reflect both the relative benefits and the
relative fault of the indemnifying party and the indemnified party in connection
with the statements or omissions that resulted in such Claims as well as any
other relevant equitable considerations. The relative benefits received by St.
Paul and the Company, on the one hand, and by the underwriters, on the other,
shall be deemed to be in the same proportion as the total net proceeds from the
offering of the securities (before deducting expenses) received by St. Paul and
the Company, on the one hand, bear to the total underwriting discounts and
commissions received by the underwriters, on the other hand, in connection with
such offering. The relative fault shall be determined by reference to, among
other things, whether the untrue or alleged untrue statement of a material fact
or the omission or alleged omission to state a material fact relates to
information supplied by the indemnifying party or by the indemnified party and
the parties' relative intent, knowledge, access to information and opportunity
to correct or prevent such statement or omission. The amount paid or payable in
respect of any Claim shall be deemed to include any legal or other expenses
reasonably incurred by such indemnified party in connection with investigating
or defending any such Claim. No person guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) is entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation.

      (e) As a condition to their obligations under this Section 2.4, each of
the Company and St. Paul must have received from each underwriter of Registrable
Shares included in a registration statement filed under the Securities Act
pursuant to Section 2.1 or 2.2 an undertaking to indemnify, to the extent
permitted by law, and hold harmless the Company and St. Paul against (or if such
indemnity is unavailable or is insufficient to hold harmless an indemnified
party, to provide contribution, on substantially the same basis provided to such
underwriter in accordance with Section 2.4(d), in respect of) any Claims to
which each such indemnified party may become subject under the Securities Act or
otherwise, insofar as such Claims arise out of or are based upon any untrue
statement or alleged untrue statement of any material fact contained in any
Registration Document, or insofar as any claims arise out of or are based upon
the omission or alleged omission to state in any Registration Document a
material fact required to be stated therein or necessary to make the statements
made therein not misleading; provided, however, that such indemnification (or
contribution, as the case may be) shall be payable only if, and to the extent
that, any such Claim arises out of or is based upon an untrue statement or
alleged untrue statement or omission or alleged omission made in any
Registration Document in reliance upon and in conformity with written
information furnished to the Company by or on behalf of such underwriter
specifically for use in the preparation thereof. Notwithstanding the foregoing,
no underwriter shall be required to contribute any amount in excess of the
amount by which the total price at which the Registrable Shares underwritten by
it and distributed to the public were offered to the public exceeds the amount
of any damages which such underwriter otherwise has been required to pay by
reason of such untrue or alleged untrue statement or omission or alleged
omission. The obligation of any underwriters to provide indemnification (or
contribution, as the case may be) pursuant to this paragraph (e) shall be
several in proportion to their respective underwriting commitments and not
joint.

      (f) The maximum liability of St. Paul to indemnify or contribute payments
pursuant to this Section 2.4 may not exceed the aggregate net proceeds from the
sale of Common Shares (including the sale


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of Common Shares, if any, pursuant to the exercise of an overallotment option)
to St. Paul in such registration.

      (g) The obligations of the Company pursuant to this Section 2.4 is in
addition to any liability which the Company may otherwise have and extends, upon
the same terms and conditions, to each officer, director and general partner of
any underwriter or St. Paul and to each person, if any, who controls any
underwriter or St. Paul within the meaning of the Securities Act. The
obligations of St. Paul pursuant to this Section 2.4 are in addition to any
liability which St. Paul may otherwise have and extends, upon the same terms and
conditions, to each officer, director and general partner of the Company, any
underwriter or any other person, if any, who controls the Company or any
underwriter within the meaning of the Securities Act. The obligations of any
underwriter pursuant to this Section 2.4 are in addition to any liability which
such underwriter may otherwise have and extends, upon the same terms and
conditions, to each officer, director and general partner of the Company or St.
Paul and to each person, if any, who controls the Company or St. Paul within the
meaning of the Securities Act.

      (h) 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.

      2.5. REQUIREMENTS WITH RESPECT TO REGISTRATION. If and whenever the
Company is required by the provisions hereof to use its reasonable best efforts
to register any Registrable Shares under the Securities Act, the Company shall,
as promptly as practicable:

            (a) Prepare and file with the SEC a registration statement with
      respect to such Registrable Shares and use its reasonable best efforts to
      cause such registration statement to become and remain effective for the
      periods specified herein.

            (b) Prepare and file with the SEC such amendments and supplements to
      such registration statement and the prospectus used in connection
      therewith as may be necessary to keep such registration statement current
      and to comply with the provisions of the Securities Act and any
      regulations promulgated thereunder with respect to the sale or other
      disposition of such Registrable Shares, for as long as a prospectus
      relating to any such Registrable Shares is required to be delivered under
      the Securities Act, subject to the limitation in Section 2.1(b)(vi).

            (c) Furnish to each member of the St. Paul Group participating in
      the offering copies (in reasonable quantities) of summary, preliminary,
      final, amended or supplemented prospectuses, in conformity with the
      requirements of the Securities Act and any regulations promulgated
      thereunder, and other documents as reasonably may be required in order to
      facilitate the disposition of such Registrable Shares, but only while the
      Company is required under the provisions hereof to keep the registration
      statement current.

            (d) Use its reasonable best efforts to register or qualify the
      Registrable Shares covered by such registration statement under such other
      securities or blue sky laws of such jurisdictions in the United States as
      the managing underwriter or placement agent (or, if none, St. Paul) shall
      reasonably request, and do any and all other acts and things which may be
      reasonably necessary to enable such managing underwriters, placement agent
      or each member of the St. Paul Group participating in the offering to
      consummate the disposition of the Registrable Shares in such
      jurisdictions; provided, however, that in no event is the Company required
      to qualify to do business as a foreign corporation


                                      -10-
<PAGE>

      in any jurisdiction where it is not so qualified; to execute or file any
      general consent to service of process under the laws of any jurisdiction;
      to take any action that would subject it to service of process in suits
      other than those arising out of the offer and sale of the securities
      covered by the registration statement; or to subject itself to taxation in
      any jurisdiction where it has not theretofore done so unless the Company
      shall have received a reasonably satisfactory indemnity in respect
      thereto; or to subject itself to any insurance regulation in any
      jurisdiction in which it has not theretofore been so subject.

            (e) Notify St. Paul, at any time when a prospectus relating to any
      Registrable Shares covered by such registration statement is required to
      be delivered under the Securities Act, of the Company's becoming aware
      that the prospectus included in such registration statement, as then in
      effect, includes an untrue statement of a material fact or omits to state
      any material fact required to be stated therein or necessary to make the
      statements therein not misleading in the light of the circumstances then
      existing, and, subject to the limitation in Section 2.1(b), promptly
      prepare and furnish to St. Paul and each underwriter a reasonable number
      of copies of a prospectus supplemented or amended so that, as thereafter
      delivered to the purchasers of the Registrable Shares, such prospectus
      shall not include an untrue statement of a material fact or omit to state
      a material fact required to be stated therein or necessary to make the
      statements therein not misleading in the light of the circumstances then
      existing.

            (f) As soon as practicable after the effective date of such
      registration statement, and in any event within eighteen (18) months
      thereafter, make generally available to St. Paul an earnings statement
      (which need not be audited) covering a period of at least twelve (12)
      consecutive months beginning after the effective date of the registration
      statement, which earning statement shall satisfy the provisions of Section
      11(a) of the Securities Act, including at the Company's option, Rule 158
      thereunder.

            (g) Deliver promptly to St. Paul, upon St. Paul's written request,
      copies of all correspondence between the SEC and the Company, its counsel
      or auditors and all memoranda relating to discussions with the SEC or its
      staff with respect to the registration statement and permit St. Paul to do
      such investigation, upon reasonable advance notice, with respect to
      information contained in or omitted from the registration statement as it
      deems reasonably necessary. St. Paul agrees that it will use its
      reasonable best efforts not to interfere unreasonably with the Company's
      business when conducting any such investigation. St. Paul shall not, and
      shall not permit any member (other than a member controlling St. Paul) of
      the St. Paul Group and shall use its reasonable best efforts to cause any
      member of the St. Paul Group controlling St. Paul and any underwriter in
      connection with such offering to, disclose any material non-public
      information received from the Company pursuant to this Section 2.5(g)
      unless such material non-public information becomes generally known on a
      non-confidential basis other than as a result of the breach of any
      obligation of confidentiality.

            (h) The Company agrees that it will use its reasonable best efforts
      to obtain "cold comfort" letters from the Company's independent public
      accountants (including one letter when such registration statement goes
      effective and one at the closing) in customary form and covering such
      matters of the type customarily covered by such "cold comfort" letters.


                                      -11-
<PAGE>

            (i) Enter into underwriting or placement agreements in the customary
      form, including, without limitation, representations and warranties and
      indemnification and contribution provisions for any underwriter or
      placement agent selling Registrable Securities hereunder.

            (j) Use its commercially reasonable efforts to qualify (and remain
      qualified) for registration on Form S-3 or F-3, as applicable.

      2.6. USE OF REGISTRATION STATEMENT. St. Paul shall, and shall cause each
other member (other than a member controlling St. Paul) of the St. Paul Group
and shall use its reasonable best efforts to cause each member of the St. Paul
Group controlling St. Paul and each underwriter in connection with any public
offering to, upon receipt by St. Paul of the Company's notice pursuant to
Section 2.5(e), promptly discontinue the disposition of Registrable Shares
pursuant to the prospectus and registration statement contemplated by such
notice, until such time as St. Paul and the underwriters have received copies of
the amended or supplemented prospectus contemplated by Section 2.5(e) and upon
such receipt by St. Paul, St. Paul shall, and shall cause each other member
(other than a member controlling St. Paul) of the St. Paul Group and shall use
its reasonable best efforts to cause each member of the St. Paul Group
controlling St. Paul and each underwriter in connection with any public offering
to, deliver to the Company all copies in the possession of any member of the St.
Paul Group or any such underwriter at the time of receipt by St. Paul of the
Company's notice pursuant to Section 2.5(e) of any prospectus covering
Registrable Shares.

      2.7. EXPENSES.

      (a) The Company shall pay (to the extent permitted by the Bermuda
Companies Act 1981 as then in effect) the Registration Expenses (other than
underwriting discounts and commissions, which shall be borne by St. Paul)
incurred in connection with the first two Demand Requests, and St. Paul shall
pay the Registration Expenses (including the underwriting discounts and
commissions) incurred in connection with all other Demand Requests, provided
that in each case, each of the Company and St. Paul shall pay the expenses of
its own legal counsel and provided further, that to the extent the Company files
a registration statement in response to a Demand Request made prior to the first
anniversary of the Closing, St. Paul will pay the Registration Expenses
(including the underwriting discounts and commissions) and such Demand Request
shall not be considered one of the first two Demand Requests for purposes of
this Section 2.7(a).

      (b) With respect to the Registration Expenses (other than underwriting
discounts and commissions, which shall be borne by St. Paul) incurred in
connection with any piggy-back registration under Section 2.2, St. Paul shall
only pay such portion of such expenses that is equal to the fraction, (i) the
numerator of which is the number of Registrable Shares registered (subject to
any cutback) pursuant to the applicable Piggy-Back Request of St. Paul, and (ii)
the denominator of which is the total number of Common Shares registered under
the applicable registration statement.

      2.8. CERTAIN OBLIGATIONS OF ST. PAUL. St. Paul shall provide such
information to the Company as the Company may reasonably request in connection
with any registration hereunder of Registrable Shares for St. Paul's account and
shall dispose of any such Registrable Shares pursuant to any registration
hereunder in the manner contemplated thereby, and shall notify the Company in
writing if it becomes aware of any material change or inaccuracy in such
information.

      2.9. TRANSFER OF ST. PAUL OPTION. In the event St. Paul transfers the St.
Paul Option to one or more transferees pursuant to Section 5(c) of the Option
Agreement, following execution by any such transferee


                                      -12-
<PAGE>

and delivery to the Company of an instrument reasonably acceptable to the
Company acknowledging that such transferee has become a party to this Agreement
and assumed its rights and obligations hereunder, all references herein to St.
Paul with respect to Registrable Shares consisting of Common Shares issuable
pursuant to the Option Agreement shall be deemed to apply (i) in the case of a
transfer of the St. Paul Option in whole, solely to the transferee of the St.
Paul Option and (ii) in the case of a transfer of the St. Paul Option in part,
collectively either to the transferees of the St. Paul Option or, if St. Paul
has retained a portion of the St. Paul Option, to St. Paul and such
transferee(s). The Company shall be entitled to rely solely upon the
instructions of St. Paul or the transferee of the St. Paul Option designated in
writing by St. Paul with respect to any rights granted hereunder to the holders
of Registrable Option Shares. The number of demand and piggy back registration
rights afforded St. Paul hereunder shall apply in aggregate to St. Paul and any
and all said transferees, without any increase in the number of said demand and
piggy back registration rights. There are no registration rights with respect to
the St. Paul Option itself.

      2.10 LOCK-UP ARRANGEMENTS. St. Paul agrees that, upon the request of the
Company, it shall agree to any lock-up arrangement requested by any underwriter
for up to a 90 day period following the effectiveness of any Securities Act
registration statement covering Capital Securities (but excluding any
registration on Form S-8 under the Securities Act or any similar successor
form), provided, that if such registration statement relates to a public
offering of Common Shares, other than pursuant to a Demand Request, St. Paul has
the right to submit a Piggy-Back Request to the Company pursuant to Section 2.2
without regard to the notice requirement in such section.

                                   ARTICLE III

                                    RULE 144

      3.1. AVAILABILITY OF RULE 144. The Company shall use its reasonable best
efforts to ensure that the information requirement set forth in paragraph (c) of
Rule 144 is satisfied so that the safe harbor provided by Rule 144 is available
to St. Paul for all transfers of Registrable Shares made after the 90th day
after the Company becomes subject to the reporting requirements of Section 13 of
the Exchange Act. Upon request made by St. Paul at any time during such period,
the Company will provide St. Paul with a written statement confirming that the
Company has been subject to and has complied with the reporting requirements as
provided in said paragraph (c), unless the Company has included such a statement
in its then-latest annual or quarterly report filed with the SEC.

                                   ARTICLE IV

                                  MISCELLANEOUS

      4.1. TERMINATION OF CERTAIN RIGHTS. The rights of St. Paul to make a
Demand Request pursuant to Section 2.1 or a Piggy-Back Request pursuant to
Section 2.2 terminate on the Termination Date; provided that, as to any
Registrable Shares that are subject to a Demand Request or Piggy-Back Request
duly delivered on or prior to the Termination Date, such termination will be
delayed until such shares have been disposed of pursuant to such registration
statement or such offering has been completed or abandoned.


                                      -13-
<PAGE>

      4.2. AMENDMENT. This Agreement may not be amended except in a written
instrument signed by the Company and St. Paul.

      4.3. 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, MN 55102
                  Attention: 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 the Company:

                  Platinum Underwriters Holdings, Ltd.
                  Clarendon House
                  2 Church Street
                  Hamilton HM11
                  Bermuda
                  Attention: General Counsel
                  Facsimile: (441) 292-4720

                  with a copy to:
                  Linda E. Ransom
                  Dewey Ballantine LLP
                  1301 Avenue of the Americas
                  New York, New York 10019
                  Facsimile: (212) 259-6333

      4.4. ENTIRE AGREEMENT. This Agreement and the Formation and Separation
Agreement constitute the entire agreement between the parties hereto with
respect to the subject matter hereof and supersede all prior agreements and
understandings, oral and written, between the parties hereto with respect to the
subject matter hereof.


                                      -14-
<PAGE>

      4.5. BINDING EFFECT; BENEFIT. This Agreement shall inure to the benefit of
and be binding upon the parties hereto, and their respective successors and
permitted assigns. Nothing in this Agreement, expressed or implied, is intended
to confer on any person other than the parties hereto, and their respective
successors and permitted assigns, any rights, remedies, obligations or
liabilities under or by reason of this Agreement.

      4.6. ASSIGNABILITY. This Agreement may not be assigned by any party
hereto, except that St. Paul may assign in whole or in part its rights and
obligations hereunder to any transferee of Registrable Securities representing
more than 4% of the outstanding Common Shares.

      4.7. HEADINGS. The headings contained in this Agreement are for
convenience only and do not affect the meaning or interpretation of this
Agreement.

      4.8. COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which is deemed to be an original and all of which
together are deemed to be one and the same instrument.

      4.9. APPLICABLE LAW; DISPUTE RESOLUTION. (a) This Agreement shall be
governed by, and construed in accordance with, the law of the State of New York
(without regard to principles of conflict of laws).

            (b) Mandatory Arbitration. The parties hereto shall promptly submit
      any dispute, claim, or controversy arising out of or relating to this
      Agreement, 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. ss.ss. 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.

            (c) 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
      (d) 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.

            (d) Injunctive Relief. This Section 4.9 shall not prevent the
      parties hereto from seeking or obtaining temporary or preliminary
      injunctive relieve in a court for any breach or threatened breach of any
      provision hereof pending the hearing before and determination of the
      Arbitrator. The parties hereby agree that they shall continue to perform
      their obligations under this Agreement pending the hearing before and
      determination of the Arbitrator, it being agreed and understood that the
      failure to so provide will cause irreparable harm to the other party
      hereto 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.


                                      -15-
<PAGE>

            (e) 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.

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

      4.11. EFFECTIVENESS. This Agreement becomes effective contingent upon the
Closing automatically and with no action on the part of any person.

<PAGE>

      IN WITNESS WHEREOF, the parties named below have hereto set their hands as
of the day and year first above written.

                                          PLATINUM UNDERWRITERS HOLDINGS, LTD.

                                          By: /s/ Jerome T. Fadden
                                              ----------------------------------
                                              Name:  Jerome T. Fadden
                                              Title: President and CEO


                                         THE ST. PAUL COMPANIES, INC.

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