UNDERWRITING AGREEMENT

Exhibit 1.1

ACE INA HOLDINGS INC.

(a Delaware corporation)

UNDERWRITING AGREEMENT

Dated: February 7, 2008

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ACE INA HOLDINGS INC.

(a Delaware corporation)

Senior and Subordinated Debt Securities

Unconditionally Guaranteed as to Payment of

Principal, Premium, if any, and Interest by

ACE LIMITED

UNDERWRITING AGREEMENT

February 7, 2008

Ladies and Gentlemen:

ACE INA Holdings Inc., a Delaware corporation (the “Company”), proposes to issue and sell up to $300,000,000 aggregate initial public offering price, or its equivalent based on the applicable exchange rate at the time of offering in such foreign or composite currencies as the Company shall designate at the time of offering, of its senior or subordinated debt securities (the “Debt Securities”), from time to time, in or pursuant to one or more offerings on terms to be determined at the time of sale. The Debt Securities will be unconditionally guaranteed as to payment of principal, premium, if any, and interest by ACE Limited, a Cayman Islands company (the “Guarantor”).

The Debt Securities will be issued in one or more series as senior indebtedness (the “Senior Debt Securities”) under an indenture, dated as of August 1, 1999 (the “Senior Indenture”), among the Company, the Guarantor and J.P. Morgan Trust Company, National Association (as successor to The First National Bank of Chicago), as trustee (the “Senior Trustee”), or as subordinated indebtedness (the “Subordinated Debt Securities”) under an indenture (the “Subordinated Indenture”, and collectively with the Senior Indenture, the “Indentures”, and each, an “Indenture”), dated as of December 1, 1999 among the Company, the Guarantor and J.P. Morgan Trust Company, National Association, as trustee (the “Subordinated Trustee”, and collectively with the Senior Trustee, the “Trustees”, and each, a “Trustee”). Each series of Debt Securities may vary, as applicable, as to title, aggregate principal amount, rank, interest rate or formula and timing of payments thereof, stated maturity date, redemption and/or repayment provisions, sinking fund requirements, conversion or exchange provisions and any other variable terms established by or pursuant to the applicable Indenture.

Whenever the Company determines to make an offering of Debt Securities, the Company and the Guarantor will enter into an agreement (each, a “Terms Agreement”) providing for the sale of such Debt Securities to, and the purchase and offering thereof by, the underwriters specified in the Terms Agreement (the “Underwriters”, which term shall include any Underwriter substituted pursuant to Section 10 hereof). The Terms Agreement relating to the offering of Debt Securities shall specify the aggregate principal amount of Debt Securities to be

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issued (the “Underwritten Securities”), the name of each Underwriter participating in such offering (subject to substitution as provided in Section 10 hereof) and the name of any Underwriter acting as co-manager in connection with such offering, the aggregate principal amount of Underwritten Securities that each such Underwriter severally agrees to purchase, whether such offering is on a fixed or variable price basis and, if on a fixed price basis, the initial offering price, the price at which the Underwritten Securities are to be purchased by the Underwriters, the form, time, date and place of delivery and payment of the Underwritten Securities and any other material variable terms of the Underwritten Securities. The Terms Agreement, which shall be substantially in the form of Exhibit A hereto, may take the form of an exchange of any standard form of written telecommunication between the Company and one or more of the Underwriters, acting for themselves and, if applicable, as representative(s) of any other Underwriters. Each offering of Underwritten Securities will be governed by this Underwriting Agreement, as supplemented by the applicable Terms Agreement. As used herein, the term “Representative(s)” means, with respect to any offering of Debt Securities, any Underwriter(s) specified as the representative(s) of the Underwriters of such offering in the applicable Terms Agreement and if none is so designated, it means the Underwriters.

The Company and the Guarantor have filed with the Securities and Exchange Commission (the “Commission”) a joint automatic shelf registration statement on Form S-3 (No. 333-130378), for the registration of the Debt Securities and the guarantee thereof of the Guarantor (the “Guarantee”) under the Securities Act of 1933, as amended (the “1933 Act”), and the offering thereof from time to time in accordance with Rule 415 of the rules and regulations of the Commission under the 1933 Act (the “1933 Act Regulations”). Such registration statement became effective automatically upon filing on December 16, 2005, each Indenture has been duly qualified under the Trust Indenture Act of 1939, as amended (the “1939 Act”), and the Company and the Guarantor have filed such post-effective amendments to such registration statement as may be required prior to the execution of the applicable Terms Agreement and each such post-effective amendment became effective automatically upon filing with the Commission. At any given time, such registration statement (as so amended, if applicable, to such time), including any required information deemed to be a part thereof at such time pursuant to Rule 430B under the 1933 Act (the “Rule 430B Information”), is referred to herein as the “Registration Statement”; and the final base prospectus or prospectuses and the final prospectus supplement relating to the offering of the Underwritten Securities, in the form first furnished to the Underwriters by the Company and the Guarantor for use in connection with the offering of the Underwritten Securities, are collectively referred to herein as the “Prospectus”; provided, however, that at any given time references to the “Registration Statement” and the “Prospectus” shall also be deemed to include all documents incorporated therein by reference pursuant to the Securities Exchange Act of 1934, as amended (the “1934 Act”), as of, in the case of the Registration Statement, such given date, or, in the case of the Prospectus, as of the date of the Prospectus. A “preliminary prospectus” shall be deemed to refer to any prospectus used before the Registration Statement became effective and any prospectus that omitted information to be included upon pricing in a form of prospectus filed with the Commission pursuant to Rule 424(b) of the 1933 Act Regulations and was used after such effectiveness and prior to the relevant Applicable Time (as defined in the applicable Terms Agreement), including in each case any base prospectus so used and the documents incorporated by reference therein. For purposes of this Underwriting Agreement, all references to the Registration Statement, Prospectus or preliminary prospectus or to any amendment or supplement to any of the foregoing shall be deemed to include any copy filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval system (“EDGAR”).

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The term “Disclosure Package” shall mean (i) each preliminary prospectus, as amended or supplemented, used in connection with the offer of the Underwritten Securities, (ii) the issuer free writing prospectuses as defined in Rule 433 of the Securities Act (each, an “Issuer Free Writing Prospectus”), if any, (iii) any other free writing prospectus that the parties hereto shall hereafter expressly agree in writing to treat as part of the Disclosure Package and (iv) the Final Term Sheet (as defined herein), which shall be identified in Schedule I to the applicable Terms Agreement.

All references in this Underwriting Agreement to financial statements and schedules and other information which is, at a given time, “contained,” “included” or “stated” (or other references of like import) in the Registration Statement, Prospectus or preliminary prospectus shall be deemed to mean and include all such financial statements and schedules and other information which is incorporated by reference or deemed to be included in the Registration Statement, Prospectus or preliminary prospectus, as the case may be, as of, in the case of the Registration Statement, such given time, or, in the case of the Prospectus, the date of the Prospectus, or, in the case of a preliminary prospectus, the relevant Applicable Time; and all references in this Underwriting Agreement to amendments or supplements to the Registration Statement, Prospectus or preliminary prospectus shall be deemed, at a given time, to mean and include the filing of any document under 1934 Act or the 1933 Act which is incorporated by reference or deemed to be included in the Registration Statement, Prospectus or preliminary prospectus, as the case may be, after, in the case of the Registration Statement, such given time, or, in the case of the Prospectus, the date of the Prospectus, or, in the case of a preliminary prospectus, the relevant Applicable Time.

SECTION 1. Representations and Warranties .

(a) Representations and Warranties by the Company and the Guarantor. The Company and the Guarantor represent and warrant to each Underwriter named in the applicable Terms Agreement, as of the date thereof, as of the Applicable Time and as of the Closing Time (as defined below) (in each case, a “Representation Date”), as follows:

(1) Compliance with Registration Requirements; Disclosure . (i) At the time of filing the Registration Statement, (ii) at the time of the most recent amendment thereto for the purposes of complying with Section 10(a)(3) of the 1933 Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Section 13 or 15(d) of the 1934 Act or form of prospectus) and (iii) at the execution time of each of this Agreement and the applicable Terms Agreement (with each such date being used as the determination date for purposes of this clause (iii)), the Company was and is a “well known seasoned issuer” as defined in Rule 405 of the 1933 Act. The Registration Statement is an “automatic shelf registration statement”, as defined in Rule 405 of the 1933 Act, neither the Company nor the Guarantor has received from the Commission any notice pursuant to Rule 401(g)(2) of the 1933 Act objecting to use of the automatic shelf registration statement form and neither the Company nor the Guarantor has otherwise ceased to be eligible to use the automatic shelf registration statement form.

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(i) At the earliest time after the filing of the Registration Statement relating to the Underwritten Securities that the Company, the Guarantor or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2) of the 1933 Act) and (ii) as of the date of the execution and delivery of each of this Agreement and the applicable Terms Agreement (with each such date being used as the determination date for purposes of this clause (ii)), neither the Company nor the Guarantor was or is an Ineligible Issuer (as defined in Rule 405 of the 1933 Act), without taking account of any determination by the Commission pursuant to Rule 405 of the 1933 Act that it is not necessary that either the Company or the Guarantor be considered an Ineligible Issuer.

No stop order has been issued under the 1933 Act and no proceedings for that purpose have been instituted or are pending or, to the knowledge of the Company or the Guarantor, are contemplated by the Commission, and any request on the part of the Commission for additional information has been complied with. In addition, each Indenture has been duly qualified under the 1939 Act.

At the respective times the Registration Statement became effective or was deemed effective with respect to the Underwriters pursuant to Rule 430B(f)(2) under the 1933 Act and at each Representation Date, the Registration Statement and any amendments thereto complied and will comply in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations and the 1939 Act and the rules and regulations of the Commission under the 1939 Act (the “1939 Act Regulations”) and did not and will not contain 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.

At the date of the Prospectus and at the Closing Time, neither the Prospectus nor any amendments and supplements thereto included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

As of the Applicable Time, the Disclosure Package did not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

Neither any Issuer Free Writing Prospectus nor the Final Term Sheet, as of its issue date and at all subsequent times through the completion of the offering of the Underwritten Securities or until any earlier date that the Company or the Guarantor notified or notifies the Representatives as described in the next sentence, did not, does not and will not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement, the Prospectus or any preliminary prospectus, including any document incorporated by reference therein that has not been superseded or modified. If at any time following issuance of an Issuer Free Writing Prospectus there occurred or occurs an event or development as a result of which such

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Issuer Free Writing Prospectus conflicted or would conflict with the information contained in the Registration Statement, the Prospectus or any preliminary prospectus, the Company has promptly notified or will promptly notify the Representatives and has promptly amended or supplemented or will promptly amend or supplement, at its own expense, such Issuer Free Writing Prospectus to eliminate or correct such conflict.

The Company has not distributed and will not distribute, prior to the later of the Closing Time and the completion of the Underwriters’ distribution of the Underwritten Securities, any offering material in connection with the offering and sale of the Underwritten Securities other than a preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus reviewed and consented to by the Representatives and included in Schedule I to the applicable Terms Agreement or the Registration Statement.

Notwithstanding the foregoing, the representations and warranties in this subsection shall not apply to statements in or omissions from the Registration Statement, the Disclosure Package or the Prospectus made in reliance upon and in conformity with information furnished to the Company or the Guarantor in writing by any Underwriter through the Representative(s) expressly for use in the Registration Statement, the Disclosure Package or the Prospectus.

To the Company’s knowledge, the Registration Statement is not the subject of a pending proceeding or examination under Section 8(d) or 8(e) of the 1933 Act, nor is the Company or the Guarantor the subject of a pending proceeding under Section 8A of the 1933 Act in connection with the offering of the Underwritten Securities.

Each preliminary prospectus and the Prospectus filed as part of the Registration Statement as originally filed or as part of any amendment thereto, or filed pursuant to Rule 424 under the 1933 Act, complied when so filed in all material respects with the 1933 Act Regulations and each preliminary prospectus and the Prospectus delivered to the Underwriters for use in connection with the offering of Underwritten Securities will, at the time of such delivery, be identical to any electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(2) Incorporated Documents . The documents incorporated or deemed to be incorporated by reference in the Registration Statement, the Disclosure Package and the Prospectus, at the time they were or hereafter are filed with the Commission, complied and will comply in all material respects with the requirements of the 1934 Act and the rules and regulations of the Commission thereunder (the “1934 Act Regulations”) and, when read together with the other information in the Disclosure Package or the Prospectus, as the case may be, at the Applicable Time or at the date of the Prospectus, as the case may be, and at the Closing Time, did not and will not include an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

(3) Independent Accountants . The accountants who certified or shall certify the financial statements and any supporting schedules thereto of the Guarantor included in each of the Registration Statement, the Disclosure Package and the Prospectus are independent public accountants with respect to the Guarantor and its subsidiaries as required by the 1933 Act and the 1933 Act Regulations.

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(4) Financial Statements . The financial statements of the Guarantor included in each of the Registration Statement, the Disclosure Package and the Prospectus, together with the related schedules and notes, as well as those financial statements, schedules and notes of any other entity included therein, present fairly the financial position of the Guarantor and its consolidated subsidiaries, or such other entity, as the case may be, at the dates indicated and the statement of operations, stockholders’ equity and cash flows of the Guarantor and its consolidated subsidiaries, or such other entity, as the case may be, for the periods specified. Such financial statements have been prepared in conformity with United States generally accepted accounting principles (“GAAP”) applied on a consistent basis throughout the periods involved, except as indicated therein or in the notes thereto. The supporting schedules, if any, included in each of the Registration Statement, the Disclosure Package and the Prospectus present fairly in accordance with GAAP the information required to be stated therein. The selected financial data and the summary financial information, if any, included in each of the Disclosure Package and the Prospectus present fairly the information shown therein and have been compiled on a basis consistent with that of the related audited financial statements included in the Registration Statement, the Disclosure Package and the Prospectus.

(5) No Material Adverse Change in Business . Since the respective dates as of which information is given in the Registration Statement, the Disclosure Package and the Prospectus, except as otherwise stated therein (i) neither the Guarantor nor any of its subsidiaries (including the Company) has sustained any material loss or material interference with its business from any action, notice, order or decree from an insurance regulatory authority and (ii) there has been (A) no material adverse change in case reserves or losses or loss expense of the Guarantor and its consolidated subsidiaries (including the Company) and (B) no material adverse change, nor any development or event involving a prospective material adverse change, in the financial condition, business, or results of operations of the Guarantor and its subsidiaries (including the Company) considered as one enterprise, in either case whether or not arising in the ordinary course of business (a “Material Adverse Change”).

(6) Good Standing of the Company . The Company has been duly incorporated and is subsisting and in good standing under the laws of the State of Delaware, with corporate power and authority to own, lease and operate its properties and to conduct its business as described in each of the Disclosure Package and the Prospectus and to enter into and perform its obligations under, or as contemplated under, this Underwriting Agreement and the applicable Terms Agreement. The Company is duly qualified to transact business as a foreign corporation and is in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so qualify or be in good standing would not reasonably be expected to result in a Material Adverse Change.

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(7) Good Standing of the Guarantor . The Guarantor has been duly incorporated and is existing and in good standing under the laws of the Cayman Islands, with corporate power and authority to own, lease and operate its properties and to conduct its business as described in each of the Disclosure Package and the Prospectus and to enter into and perform its obligations under, or as contemplated under, this Underwriting Agreement and the applicable Terms Agreement. The Guarantor is duly qualified to transact business as a foreign corporation and is in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so qualify or be in good standing would not reasonably be expected to result in a Material Adverse Change.

(8) Good Standing of Corporate Subsidiaries . Each subsidiary of the Guarantor, other than such subsidiaries as would not, individually or in the aggregate, constitute a “significant subsidiary” as such term is defined in Rule 1-02 of Regulation S-X promulgated under the 1933 Act (each, a “Significant Subsidiary”) (including the Company) that is a corporation has been duly incorporated or organized and is an existing corporation in good standing (with respect to jurisdictions that recognize such concept) under the laws of the jurisdiction of its incorporation, with corporate power and authority to own, lease and operate its properties and to conduct its business as described in each of the Disclosure Package and the Prospectus; and each such Significant Subsidiary of the Guarantor is duly qualified to transact business as a foreign corporation and is in good standing (with respect to jurisdictions that recognize such concept) in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so qualify or be in good standing would not reasonably be expected to result in a Material Adverse Change; all of the issued and outstanding capital stock of each such Significant Subsidiary of the Guarantor has been duly authorized and validly issued and is fully paid and nonassessable; and all of the issued and outstanding capital stock of each such Significant Subsidiary is owned by the Guarantor, directly or through subsidiaries, except for de minimis shareholdings as required to comply with applicable law, and such capital stock is owned free and clear of any security interest, mortgage, pledge, lien, encumbrance, claim or equity (except for restrictions on transferability of the shares of insurance subsidiaries, under applicable law).

(9) Good Standing of Partnership Subsidiaries . Each Significant Subsidiary of the Guarantor that is a partnership has been duly formed and is an existing partnership in good standing (with respect to jurisdictions that recognize such concept) under the laws of the jurisdiction of its formation, with power and authority to own, lease and operate its properties and to conduct its business as described in each of the Disclosure Package and the Prospectus; and each such Significant Subsidiary of the Guarantor is duly qualified to transact business and is in good standing (with respect to jurisdictions that recognize such concept) in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so qualify or be in good standing would not reasonably be expected to result in a Material Adverse Change; all of the outstanding equity interests of each such Significant Subsidiary of the Guarantor have been duly authorized and validly issued; and all of the equity interests of each such Significant Subsidiary are owned by the Guarantor,

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directly or through subsidiaries, free and clear of any security interest, mortgage, pledge, lien, encumbrance, claim or equity (other than immaterial amounts necessary to comply with applicable law).

(10) Capitalization . If the Disclosure Package or the Prospectus contains a “Capitalization” section, the authorized, issued and outstanding shares of capital stock of the Guarantor are as set forth in the column entitled “Actual” under such section (except for subsequent issuances thereof, if any, pursuant to reservations, agreements or employee benefit plans or pursuant to the exercise of convertible securities or options). Such shares of capital stock have been duly authorized and validly issued by the Guarantor and are fully paid and non-assessable, and none of such shares of capital stock was issued in violation of preemptive or other similar rights of any securityholder of the Guarantor.

(11) Authorization of this Underwriting Agreement and Terms Agreement . This Underwriting Agreement has been, and the applicable Terms Agreement as of the date thereof will have been, duly authorized, executed and delivered by each of the Company and the Guarantor.

(12) Authorization of Underwritten Securities . The Underwritten Securities have been, or as of the date of the applicable Terms Agreement will have been, duly authorized by the Company for issuance and sale pursuant to this Underwriting Agreement and such Terms Agreement. Such Underwritten Securities, when issued and authenticated in the manner provided for in the applicable Indenture and delivered against payment of the consideration therefor specified in such Terms Agreement, will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms, except as the enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or other similar laws affecting the enforcement of creditors’ rights generally or by general equitable principles (regardless of whether enforcement is considered in a proceeding in equity or at law), and except further as enforcement thereof may be limited by requirements that a claim with respect to any Underwritten Securities payable in a foreign or composite currency (or a foreign or composite currency judgment in respect of such claim) be converted into U.S. dollars at a rate of exchange prevailing on a date determined pursuant to applicable law or by governmental authority to limit, delay or prohibit the making of payments outside the United States. Such Underwritten Securities will be in the form contemplated by, and each registered holder thereof will be entitled to the benefits of, the applicable Indenture.

(13) Authorization of Guarantee . The Guarantee has been, or as of the date of such Terms Agreement will have been, duly authorized by the Guarantor for issuance pursuant to this Underwriting Agreement and the applicable Terms Agreement. Such Guarantee, when issued and delivered in the manner provided for in the applicable Indenture, will constitute a valid and binding obligation of the Guarantor, enforceable against the Guarantor in accordance with its terms, except as the enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or other similar laws

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affecting the enforcement of creditors’ rights generally or by general equitable principles (regardless of whether enforcement is considered in a proceeding in equity or at law), and will be in the form contemplated by, and entitled to the benefits of, the Indenture.

(14) Authorization of the Indentures . The applicable Indenture has been, or prior to the issuance of the Debt Securities thereunder will have been, duly authorized, executed and delivered by the Company and the Guarantor and, upon such authorization, execution and delivery, will constitute a valid and binding agreement of the Company and the Guarantor, enforceable against each of them in accordance with its terms, except as the enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or other similar laws affecting the enforcement of creditors’ rights generally or by general equitable principles (regardless of whether enforcement is considered in a proceeding in equity or at law).

(15) Descriptions of the Underwritten Securities, the Guarantee and the Indentures . The Underwritten Securities being sold pursuant to the applicable Terms Agreement, the Guarantee and each applicable Indenture, as of each Representation Date, will conform in all material respects to the statements relating thereto contained in each of the Disclosure Package and the Prospectus and will be in substantially the form filed or incorporated by reference, as the case may be, as an exhibit to the Registration Statement.

(16) Non-Taxation of Interest . Except as disclosed in the Disclosure Package and the Prospectus, under current laws and regulations of the Cayman Islands and Bermuda and any political subdivision thereof, all interest payable on the Underwritten Securities may be paid by the Guarantor pursuant to the Guarantee to the holders thereof in United States dollars and freely transferred out of the Cayman Islands or Bermuda and all such payments made to holders thereof or therein who are non-residents of the Cayman Islands or Bermuda will not be subject to income, withholding or other taxes under laws and regulations of the Cayman Islands or Bermuda or any political subdivision or taxing authority thereof or therein and will otherwise be free and clear of any other tax, duty, withholding or deduction in the Cayman Islands or Bermuda or any political subdivision or taxing authority thereof or therein and without the necessity of obtaining any governmental authorization in the Cayman Islands or Bermuda or any political subdivision or taxing authority thereof or therein.

(17) Reserves . The description of the Guarantor’s reserves and reserving methodology and assumptions described in each of the Disclosure Package and the Prospectus is accurate and fairly presents the information set forth therein in all material respects and, since the date of the latest financial statements included in each of the Disclosure Package and the Prospectus, no loss experience has developed which would require or make it appropriate for the Guarantor to alter or modify such methodology.

(18) Absence of Defaults and Conflicts . Neither the Guarantor or any of its subsidiaries (including the Company) is in violation of its charter or by-laws, partnership agreement or other constitutive documents or in default in the performance or observance

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of any obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, deed of trust, loan or credit agreement, note, lease or other agreement or instrument to which the Guarantor or any of its subsidiaries (including the Company) is a party or by which it or any of them may be bound, or to which any of the assets, properties or operations of the Guarantor or any of its subsidiaries (including the Company) is subject (collectively, “Agreements and Instruments”), except for such defaults that would not reasonably be expected to result in a Material Adverse Change. The execution, delivery and performance of this Underwriting Agreement, the applicable Terms Agreement and each applicable Indenture and any other agreement or instrument entered into or issued or to be entered into or issued by the Company or the Guarantor in connection with the transactions contemplated hereby or thereby or in the Registration Statement, the Disclosure Package and the Prospectus, and the consummation of the transactions contemplated herein and in the Registration Statement, the Disclosure Package and the Prospectus (including, without limitation, the issuance and sale of the Underwritten Securities, the issuance of the Guarantee, and the use of the proceeds from the sale of the Underwritten Securities, together with the Guarantee, as described under the caption “Use of Proceeds”) and compliance by the Company and the Guarantor, as applicable, with their respective obligations hereunder and thereunder have been duly authorized by all necessary corporate action and do not and will not, whether with or without the giving of notice or passage of time or both, conflict with or constitute a breach of, or default or Repayment Event (as defined below) under, or result in the creation or imposition of any lien, charge or encumbrance upon any assets, properties or operations of the Guarantor or any of its subsidiaries (including the Company) pursuant to, any Agreements and Instruments (except for such conflicts, breaches, defaults or Repayment Events or liens, charges or encumbrances that would not reasonably be expected to result in a Material Adverse Change), nor will such action result in any violation of the provisions of the charter, by-laws, partnership agreement or other constitutive document of the Guarantor or any of its subsidiaries (including the Company) or, to the best of the Company’s and the Guarantor’s knowledge, any applicable law, statute, rule, regulation, judgment, order, writ or decree of any government, government instrumentality or court, domestic or foreign, having jurisdiction over the Guarantor or any of its subsidiaries (including the Company) or over any of the assets, properties or operations of the Guarantor or any of its subsidiaries (including the Company), except for such violations under applicable law, statute, rule, regulation, judgment, order, writ or decree as would not reasonably be expected to result in a Material Adverse Change. As used herein, a “Repayment Event” means any event or condition that gives the holder of any note, debenture or other evidence of indebtedness (or any person acting on such holder’s behalf) the right to require the repurchase, redemption or repayment of all or a portion of such indebtedness by the Guarantor or any of its subsidiaries (including the Company).

(19) Absence of Proceedings . There is no action, suit, proceeding, inquiry or investigation before or brought by any court or governmental agency or body, domestic or foreign, now pending, or to the knowledge of the Company or the Guarantor threatened or contemplated, against or affecting the Guarantor or any of its subsidiaries (including the Company) that is required to be disclosed in the Registration Statement, the Disclosure Package or the Prospectus (other than as stated therein), or that would

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reasonably be expected to result in a Material Adverse Change, or that would reasonably be expected to materially and adversely affect the ability of the Company or the Guarantor to perform its obligations under this Agreement or the applicable Terms Agreement.

(20) Accuracy of Exhibits . There are no contracts or documents that are required to be described in the Registration Statement, the Disclosure Package, the Prospectus or the documents incorporated by reference therein or to be filed as exhibits thereto that have not been so described and filed as required.

(21) Absence of Further Requirements . No consent, approval, authorization, or order of, or filing with, any governmental agency or body or any court, domestic or foreign, is required for the due authorization, execution or delivery by the Company or the Guarantor of this Underwriting Agreement or the applicable Terms Agreement or for the performance by the Company or the Guarantor of the transactions contemplated under the Prospectus, this Underwriting Agreement, such Terms Agreement or the applicable Indenture, as applicable, except such as have been obtained and made under the 1933 Act, such filing of the Prospectus as has been made with the Bermuda Registrar of Companies under the Companies Act 1981 of Bermuda and such as may be required under state securities laws.

(22) Possession of Licenses and Permits . The Guarantor and its subsidiaries (including the Company) possess such permits, licenses, approvals, consents and other authorizations (collectively, “Governmental Licenses”) issued by the appropriate federal, state, local or foreign regulatory agencies or bodies necessary to conduct the business now operated by them, except where the failure to so possess any such Governmental Licenses would not, singly or in aggregate, reasonably be expected to result in a Material Adverse Change. The Guarantor and its subsidiaries (including the Company) are in compliance with the terms and conditions of all such Governmental Licenses, except where the failure so to comply would not, singly or in the aggregate, reasonably be expected to result in a Material Adverse Change. All of the Governmental Licenses are valid and in full force and effect, except where the invalidity of such Governmental Licenses or the failure of such Governmental Licenses to be in full force and effect would not reasonably be expected to result in a Material Adverse Change. Neither the Guarantor nor any of its subsidiaries (including the Company) has received any notice of proceedings relating to the revocation or modification of any such Governmental Licenses that, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would reasonably be expected to result in a Material Adverse Change.

(23) Insurance Laws . Each of the Guarantor and its insurance subsidiaries (including insurance holding companies) is duly registered, licensed or admitted as an insurer or an insurance holding company (as applicable) in each jurisdiction where it is required to be so licensed or admitted to conduct its business as presently conducted, except where the failure to be so registered, licensed or admitted would not reasonably be expected to result in a Material Adverse Change; each of the Guarantor and its insurance subsidiaries has all other necessary authorizations, approvals, orders, certificates and permits, of and from, and has made all declarations and filings with, all insurance

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authorities, commissions or other insurance regulatory bodies to conduct their respective businesses as described in each of the Disclosure Package and the Prospectus, except for where the failure to have such authorizations, approvals, orders, certificates and permits, or to make such declarations and filings, would not reasonably be expected to result in a Material Adverse Change; all of such authorizations, approvals, orders, certificates and permits are in full force and effect, except where the failure to be in full force and effect would not reasonably be expected to result in a Material Adverse Change; and neither the Guarantor nor its insurance subsidiaries has received any notification from any insurance authority, commission or other insurance regulatory body to the effect that any additional authorization, approval, order, license, certificate or permit from such authority, commission or body is needed to be obtained by any of the Guarantor or its insurance subsidiaries, except for any authorization, approval, order, license, certificate or permit from any such authority, commission or body the failure of which to obtain, singly or in the aggregate, would not reasonably be expected to result in a Material Adverse Change. Each of the Guarantor and its insurance subsidiaries is in compliance with all applicable insurance statutes and regulations and has filed all reports, documents or other information required to be filed under such statutes and regulations, except where the failure to comply or file would not reasonably be expected to result in a Material Adverse Change; and each of the Guarantor and its insurance subsidiaries is in compliance with the insurance laws and regulations of other jurisdictions which are applicable to the Guarantor and its insurance subsidiaries (as the case may be), except where the failure to comply would not reasonably be expected to result in a Material Adverse Change.

(24) Governmental Authorization . Except as set forth in the Registration Statement, the Disclosure Package and the Prospectus, no authorization, approval or consent of any governmental authority or agency is required (other than any license as an insurer or insurance holding company and other than those that have already been obtained) under the laws of any jurisdiction in which the Guarantor or any of its subsidiaries (including the Company) conduct their respective businesses in connection with the ownership, directly or indirectly, by the Guarantor of equity interests in any subsidiary (including the Company) or the repatriation of any amount from or to the Guarantor or any of its subsidiaries (including the Company), except to the extent that the failure to obtain such authorization, approval or consent would not reasonably be expected to result in a Material Adverse Change.

(25) Commodity Exchange Act . The Underwritten Securities, upon issuance, will be excluded or exempted under, or beyond the purview of, the Commodity Exchange Act, as amended (the “Commodity Exchange Act”), and the rules and regulations of the Commodity Futures Trading Commission under the Commodity Exchange Act (the “Commodity Exchange Act Regulations”).

(26) Investment Company Act . The Company and the Guarantor are not, and upon the issuance and sale of the Underwritten Securities as herein contemplated and the application of the net proceeds therefrom as described in each of the Disclosure Package and the Prospectus they will not be, an “investment company” within the meaning of the Investment Company Act of 1940, as amended (the “1940 Act”).

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(27) Internal Controls and Procedures . The Guarantor maintains a system of internal control over financial reporting (as such term is defined in Rule 13a-15(f) under the Exchange Act) designed by, or under the supervision of, the Company’s principal executive officer and principal financial officer to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. The Guarantor’s internal control over financial reporting was effective as of the end of the quarter ended December 31, 2006, and the Guarantor was not aware of any material weaknesses in its internal control over financial reporting at such time.

(b) Officers’ Certificates. Any certificate signed by any officer of the Company, the Guarantor or any of their respective subsidiaries and delivered to the Representative(s) or to counsel for the Underwriters in connection with the offering of the Underwritten Securities shall be deemed a representation and warranty by the Company, the Guarantor or such subsidiary, as the case may be, to each Underwriter as to the matters covered thereby on the date of such certificate and, unless subsequently amended or supplemented, at each Representation Date subsequent thereto.

SECTION 2. Sale and Delivery to Underwriters; Closing .

(a) Underwritten Securities. The several commitments of the Underwriters to purchase the Underwritten Securities pursuant to the applicable Terms Agreement shall be deemed to have been made on the basis of the representations, warranties and agreements herein contained and shall be subject to the terms and conditions herein set forth.

(b) Payment. Payment of the purchase price for, and delivery of, the Underwritten Securities shall be made at the offices of Sidley Austin LLP , 787 Seventh Avenue, New York, New York 10019, or at such other place as shall be agreed upon by the Representative(s) and the Company, at 9:00 A.M. (Eastern time) on the third (fourth, if the pricing occurs after 4:30 P.M. (Eastern time) on any given day) business day after the date of the applicable Terms Agreement (unless postponed in accordance with the provisions of Section 10 hereof), or such other time not later than ten business days after such date as shall be agreed upon by the Representative(s) and the Company (such time and date of payment and delivery being herein called “Closing Time”).

Payment shall be made to the Company by wire transfer of immediately available funds to a bank account designated by the Company, against delivery to the Representative(s) for the respective accounts of the Underwriters of the Underwritten Securities to be purchased by them. It is understood that each Underwriter has authorized the Representative(s), for its account, to accept delivery of, receipt for, and make payment of the purchase price for, the Underwritten Securities which it has severally agreed to purchase. Any Representative, individually and not as representative of the Underwriters, may (but shall not be obligated to) make payment of the purchase price for the Underwritten Securities to be purchased by any Underwriter whose funds have not been received by the Closing Time, but such payment shall not relieve such Underwriter from its obligations hereunder.

(c) Denominations; Registration. If the Underwritten Securities are issued other than in book-entry form, certificates for the Underwritten Securities shall be in such denominations and

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registered in such names as the Representative(s) may request in writing at least one full business day prior to the Closing Time. If the Underwritten Securities are issued other than in book-entry form, certificates for the Underwritten Securities will be made available for examination and packaging by the Representative(s) in The City of New York not later than 10:00 A.M. (Eastern time) on the business day prior to the Closing Time.

SECTION 3. Covenants of the Company and the Guarantor . The Company and the Guarantor covenant with the Representative(s) and with each Underwriter participating in the offering of Underwritten Securities, as follows:

(a) Compliance with Securities Regulations and Commission Requests; Payment of Filing Fees. The Company and the Guarantor, subject to Section 3(b), will comply with the requirements of Rule 430B of the 1933 Act Regulations, if and as applicable, and they will notify the Representative(s) immediately, and confirm the notice in writing, of (i) the filing and effectiveness of any post-effective amendment to the Registration Statement or the filing of any supplement or amendment to the Prospectus, (ii) the receipt of any comments from the Commission, (iii) any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to the Prospectus or for additional information, (iv) the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any order preventing or suspending the use of any preliminary prospectus, or of the suspension of the qualification of the Underwritten Securities for offering or sale in any jurisdiction, or of the initiation or threatening of any proceedings for any of such purposes or of any examination pursuant to Section 8(e) of the 1933 Act concerning the Registration Statement and (v) if the Company or the Guarantor becomes the subject of a proceeding under Section 8A of the 1933 Act in connection with the offering of the Underwritten Securities. The Company and the Guarantor will effect the filings required under Rule 424(b) of the 1933 Act Regulations, in the manner and within the time period required by Rule 424(b) (without reliance on Rule 424(b)(8)), and will take such steps as they deem necessary to ascertain promptly whether each preliminary prospectus and the Prospectus transmitted for filing under Rule 424 was received for filing by the Commission and, in the event that it was not, they will promptly file such preliminary prospectus or the Prospectus. The Company and the Guarantor will make every reasonable effort to prevent the issuance of any stop order and, if any stop order is issued, to obtain the lifting thereof at the earliest possible moment. The Company and the Guarantor agree to pay the required Commission filing fees relating to the Underwritten Securities within the time required by Rule 456(b)(1) of the 1933 Act Regulations without regard to the proviso therein and otherwise in accordance with Rules 456(b) and 457(r) of the 1933 Act Regulations.

(b) Filing of Amendments and Exchange Act Documents; Preparation of Final Term Sheet . The Company and the Guarantor will give the Representative(s) notice of their intention to file or prepare any amendment to the Registration Statement or any amendment, supplement or revision to either any preliminary prospectus or to the Prospectus, whether pursuant to the 1933 Act, the 1934 Act or otherwise, and the Company and the Guarantor will furnish the Representative(s) with copies of any such documents a reasonable amount of time prior to such proposed filing or use, as the case may be, and will give the Representative(s) a reasonable opportunity to comment on any such document prior to such proposed filing or use, as the case may be. The Company will prepare a final term sheet (the “Final Term Sheet”) reflecting the

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final terms of the Underwritten Securities, in form and substance satisfactory to the Representative(s) and attached as Schedule II to the applicable Terms Agreement, and shall file such Final Term Sheet as an “issuer free writing prospectus” pursuant to Rule 433 under the 1933 Act Regulations within the time required by such rule.

(c) Delivery of Registration Statements. The Company and the Guarantor have furnished or will deliver to the Representative(s) and counsel for the Underwriters, without charge, signed copies of the Registration Statement as originally filed and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein and documents incorporated or deemed to be incorporated by reference therein or deemed to be a part thereof) and signed copies of all consents and certificates of experts, and will also deliver to the Representative(s), without charge, a conformed copy of the Registration Statement as originally filed and of each amendment thereto (without exhibits) for each of the Underwriters. The Registration Statement and each amendment thereto furnished to the Underwriters will be identical to any electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(d) Delivery of Prospectuses. The Company and the Guarantor will deliver to each Underwriter, without charge, as many copies of each preliminary prospectus and each Permitted Free Writing Prospectus (as defined below) as such Underwriter may reasonably request, and the Company and the Guarantor hereby consent to the use of such copies for purposes permitted by the 1933 Act. The Company and the Guarantor will furnish to each Underwriter, without charge, during the period when the Prospectus is required to be delivered under the 1933 Act or the 1934 Act, such number of copies of the Prospectus as such Underwriter may reasonably request. The Prospectus and any amendments or supplements thereto furnished to the Underwriters will be identical to any electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(e) Continued Compliance with Securities Laws. The Company and the Guarantor will comply with the 1933 Act and the 1933 Act Regulations and the 1934 Act and the 1934 Act Regulations so as to permit the completion of the distribution of the Underwritten Securities as contemplated in this Underwriting Agreement and the applicable Terms Agreement and in the Registration Statement and the Prospectus. If at any time when the Prospectus is required by the 1933 Act or the 1934 Act to be delivered in connection with sales of the Underwritten Securities, any event shall occur or condition shall exist as a result of which it is necessary, in the opinion of counsel for the Underwriters or for the Company and the Guarantor, to amend the Registration Statement in order that the Registration Statement will not contain 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 or to amend or supplement the Prospectus in order that the Prospectus will not include an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein not misleading in the light of the circumstances existing at the time it is delivered to a purchaser, or if it shall be necessary, in the opinion of such counsel, at any such time to amend the Registration Statement or amend or supplement the Prospectus in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company and the Guarantor will promptly prepare and file with the Commission, at its own expense, subject to Section 3(b), such amendment or supplement as may be necessary to correct such statement or omission or to comply with such requirements, the

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Company and the Guarantor will use their best efforts to have such amendment declared effective as soon as practicable (if it is not automatically effective with respect to the Underwritten Securities), and the Company and the Guarantor will furnish to the Underwriters, without charge, such number of copies of such amendment or supplement as the Underwriters may reasonably request. Neither the Representa