AGREEMENT FOR THE SALE AND PURCHASE OF CERTAIN ASSETS OF THE UK REINSURANCE BUSINESS OF ARTHUR J. GALLAGHER

Exhibit 10.45

ARTHUR J. GALLAGHER (UK) LIMITED

AND

AON LIMITED

AND

ARTHUR J. GALLAGHER & CO

AGREEMENT FOR THE SALE

AND PURCHASE OF CERTAIN ASSETS OF THE UK

REINSURANCE BUSINESS OF ARTHUR J. GALLAGHER

(UK) LIMITED

CONTENTS

Schedule 1 E XCLUDED A SSETS A ND L IABILITIES

Part A Excluded Assets

Part B Excluded Liabilities

Schedule 2 D EFERRED C ONSIDERATION

Schedule 3 C LOSING R EQUIREMENTS

Schedule 4 W ARRANTIES

Part A Seller’s Warranties

Part B Buyer’s Warranties

Schedule 5 E MPLOYEES

Part A Transferring Employees

Part A1 Specified Key Employees

Part B Non-Transferring Employees

Part C Retention Bonuses

Schedule 6 C EDANTS

Schedule 7 L IMITATIONS O N W ARRANTY C LAIMS

Schedule 8 P ROGRAMMES

Schedule 9 P ROSPECTS

Schedule 10 A CCOUNTS D ETAILS

Part A Accounts Receivable And Payable

Part B Custodial, Trust And Fiduciary Accounts

Schedule 11 O WNED I NTELLECTUAL P ROPERTY R IGHTS

Schedule 12 T HIRD P ARTY P AYEES

Schedule 13 T UCKER D OMAIN N AMES

Agreed Form Documents

THIS AGREEMENT is made on 22 February 2008

BETWEEN:

THE PARTIES AGREE as follows:

“ Act ” means the Companies Act 1985

“ Assets ” means all the property and assets agreed to be sold and purchased under this Agreement as described in clause 2.1;

“ Bartell Patent Deed of Assignment ” means the patent deed of assignment between Martin Bartell and Aon Capital Markets Limited, in the agreed form;

“ Business ” means the business of broking reinsurance business, as carried out by the Seller in the United Kingdom for the Cedants in respect of the Programmes, and the Re-Ex Business;

“ Business Day ” means a day other than a Saturday or Sunday or public holiday in England and Wales;

“ Buyer’s Group Undertaking ” means the Buyer or an undertaking which is, on or at any time after the date of this Agreement, a subsidiary undertaking or parent undertaking of the Buyer;

“ Buyer’s Solicitors ” means Clifford Chance Limited Liability Partnership of 10 Upper Bank Street, London E14 5JJ;

“ Buyer Warranty ” means a statement contained in Part B of Schedule 4 and “ Buyer Warranties ” means all of those statements;

“ CASS ” means the Client Asset Source Book of the FSA Handbook of Rules and Regulations (as amended from time to time);

“ Cedants ” means certain clients of the Seller to whom the Seller provides reinsurance broking services, as set out in Schedule 6;

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“ Client Money Transfer Deed ” means the client money transfer deed, in the agreed form;

“ Closing ” means completion of the sale and purchase of the Business and the Assets in accordance with this Agreement;

“ Closing Date ” means the later of 25 March 2008 and the date (not being later than 30 April 2008) on which the last of the Conditions to be satisfied or waived is satisfied or waived;

“ Compromise Agreement ” has the meaning given to it in clause 9.5;

“ Condition ” means a condition set out in clause 3 and “ Conditions ” means all those conditions;

“ Confidential Information ” means all information which is used in or otherwise relates to the Business, the Assets or customers or financial or other affairs of the Seller in relation to the Business and all information which relates to the business, financial or other affairs of the Buyer including in each case information relating to:

but does not include information which is or becomes publicly available (other than as a result of the Seller’s breach of this Agreement) or disclosed with the written consent of the Buyer;

“ Contingent Purchase Price ” has the meaning given to it in Schedule 2;

“ Effective Time ” means 17.00 on the Closing Date or such other time as is agreed in writing between the Buyer and the Seller;

“ Encumbrance ” means a mortgage, charge, pledge, lien, option, restriction, right of first refusal, right of pre-emption, any other third party right or interest having similar effect, other encumbrance or security interest of any kind (not being one arising by operation of law), or another type of preferential arrangement (including a title transfer or retention arrangement) having similar effect;

“ Excluded Assets ” means the assets set out in Part A of Schedule 1;

“ Excluded Liabilities ” means the liabilities set out in Part B of Schedule 1;

“ FSA ” means the UK Financial Services Authority;

“ Goodwill ” means the goodwill of the Business and the right for the Buyer to represent itself as operating the Business in succession to the Seller;

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“ HMRC ” means HM Revenue and Customs or such authority as may succeed it in its functions relating to VAT;

“ IBA Balances ” means the IBA Consent Balances and the IBA Non-Consent Balances;

“ IBA Consent Balances ” means all amounts outstanding on the Seller’s client, trust or fiduciary account as at the IBA Transfer Date in respect of the Business, including for the avoidance of doubt funds held by the Seller as agent for Underwriters in respect of which consent to the transfer of such balances to the Buyer has been received;

“ IBA Non-Consent Balances ” means all amounts outstanding on the Seller’s client, trust or fiduciary accounts as at the IBA Transfer Date in respect of the Business, including for the avoidance of doubt funds held by the Seller as agent for Underwriters and client monies in respect of which consent to the transfer of such balances to the Buyer has not been received;

“ IBA Debits ” means those amounts that have accrued and are payable by any Cedants, Underwriters or intermediaries via the Seller as at the Effective Time in respect of the Business (as set out in the IBA Ledger Account) including any unmatched cash debit items;

“ IBA Credits ” means those amounts that have accrued and are payable to any Cedants, Underwriters or intermediaries via the Seller as at the Effective Time in respect of the Business (as set out in the IBA Ledger Account) including any unmatched cash credit items;

“ IBA Ledger Account ” means the account established and maintained by the Seller for the purpose of recording business transacted by the Seller for the benefit of any Cedants, Underwriters or intermediaries and showing, inter alia, the corresponding IBA Debits and IBA Credits in respect of the Business;

“ IBA Funding Shortfall ” means an amount which has been advanced by the Seller to any Cedant, Underwriter or intermediary in respect of which the corresponding IBA Debit has not been received and which is not capable of being offset by other cash held on the Buyer’s relevant client money account for the benefit of such Cedant, Underwriter or intermediary;

“ IBA Schedule ” has the meaning given to it in clause 11.8;

“ IBA Shortfall ” means the amount by which an IBA Credit exceeds the amount that has been received by the Buyer in respect of the corresponding IBA Debit at the time such IBA Credit is due and payable;

“ IBA Transfer Date ” means the date on which the Transitional Support Period expires or such earlier date as may be agreed between the parties;

“ Indemnified Party ” and “ Indemnifier ” have the meaning given to them in clause 17.10;

“ Initial Contingent Purchase Price ” has the meaning given to it in Schedule 2;

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“ Intellectual Property ” means all intellectual and industrial property rights wherever subsisting in the world including, without limitation:

“ Intellectual Property Deed of Assignment ” means the deed of assignment of intellectual property between the Seller and a Buyer’s Group Undertaking, in the agreed form;

“ Key Employees ” has the meaning given to it in clause 9.1;

“ Licensed In Intellectual Property Rights ” means all Intellectual Property relevant to the Business owned by a third party of which a Seller’s Group Undertaking has a licence, including, without limitation, the Intellectual Property the subject of the PCS Licence Agreement;

“ Non-Transferring Employees ” has the meaning given to it in clause 9.1;

“ NYMEX ” means the New York Mercantile Exchange, Inc;

“ NYMEX Licence Agreement ” means the licence agreement dated 11 December 2006 between the Seller and New York Mercantile Exchange, Inc.;

“ NYMEX Licence Novation Agreement ” means an agreement pursuant to which the Seller’s rights and obligations under the NYMEX Licence Agreement are novated to a Buyers’ Group Undertaking, in a form acceptable to the Buyer;

“ Ordinary Course of Business ” means with respect to actions and operations conducted by the Seller, actions and operations that are (a) consistent with the past practices of the Seller as they relate to the Assets and (b) taken in the ordinary course of the normal, day-to-day operations of the Business;

“ Owned Intellectual Property Rights ” means all Intellectual Property owned (wholly or partly) by the Seller or another Seller’s Group Undertaking and used or held for use exclusively in connection with the Business at the Effective Time (including the Intellectual Property identified in Schedule 11);

“ PCS Licence Agreement ” means the licence agreement dated 6 November 2006 between ISO Services, Inc. and the Buyer;

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“ PCS Licence Novation Agreement ” means an agreement pursuant to which the Seller’s rights and obligations under the PCS Licence Agreement are novated to a Buyer’s Group Undertaking, in a form acceptable to the Buyer;

“ Post-Closing Liabilities ” means all outgoings (including periodic outgoings), expenses, liabilities, obligations, debts, Tax and commitments incurred in connection with the Business and the Assets after and including the Effective Time, excluding, for the avoidance of doubt, the Excluded Liabilities;

“ Pre-Closing Liabilities ” means all outgoings (including periodic outgoings), expenses, liabilities, obligations, debts, Tax and commitments incurred in connection with the Business and the Assets before and excluding the Effective Time, whether or not due and payable and whether or not invoiced or notified to the Business before the Effective Time excluding, for the avoidance of doubt, the Post-Closing Liabilities and the Run-Off Liabilities;

“ Programmes ” means the reinsurance programmes set out in Schedule 8;

“ Prospects ” means the clients and contracts representing UK pipeline revenue, as set out in Schedule 9;

“ Records ” means the Seller’s books and records relating exclusively to the Business and the Assets (including all such records in relation to the Cedants, Underwriters, current customers, third party insurance administration service providers and the Owned and Licensed In Intellectual Property Rights and invoices and including the IBA Ledger Account);

“ Relevant Claim ” means a claim by the Buyer under this Agreement;

“ Re-Ex Business ” means the Licence Agreement, the PCS Licence Agreement and the associated arrangements and the revenue due to the Seller pursuant to the terms of those agreements;

“ Run-Off Liabilities ” means the costs and expenses associated with the administration after Closing of the run-off for current and prior years in respect of Cedants that have an in-force treaty among the Programmes, for the same class of business as the in-force treaty, whether or not invoiced and whether or not due and payable at that time and excluding, for the avoidance of doubt, the Excluded Liabilities. For the purposes of this definition, “class of business” means (a) speciality property treaty, (b) casualty treaty, (c) life and accident & health treaty or (d) facultative;

“ Seller Warranty ” means a statement contained in Part A of Schedule 4 and “ Seller Warranties ” means all those statements;

“ Seller’s Bank Account ” means the bank account at Barclays Bank PLC, account number 55482600, sort code 20-00-00, IBAN no GB83BARC20000055482600, swift code BARCGB22;

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“ Seller’s Group Undertaking ” means the Seller or an undertaking which is, from time to time after the date of this Agreement, a subsidiary undertaking or parent undertaking of the Seller or a subsidiary undertaking of a parent undertaking of the Seller;

“ Singapore Confidential Information ” has the meaning given to it in clause 14.3;

“ Specified Key Employees ” has the meaning given to it in clause 9.1;

“ Tax ” means any form of taxation, levy, duty, charge, contribution, withholding or impost in the nature of taxation (including any related fine, penalty, surcharge or interest) imposed, collected or assessed by, or payable to, a Tax Authority;

“ Tax Authority ” means any government, state or municipality or any local, state, federal or other authority, body or official anywhere in the world exercising a fiscal, revenue, customs or excise function including HMRC;

“ Taxes Act ” means the Income and Corporation Taxes Act 1988;

“ TOGC ” means the transfer of a business or part of a business as a going concern for the purposes of section 49 of the VAT Act and article 5 of the Value Added Tax (Special Provisions) Order 1995;

“ Transferring Employees ” has the meaning given to it in clause 9.1;

“ Transitional Support Agreement ” means the agreement in the agreed form to be entered into by the Buyer and the Seller at Closing setting out the support services to be provided by the Seller to the Buyer during the Transitional Support Period;

“ Transitional Support Period ” means the period commencing on Closing and ending 60 days after Closing;

“ Tucker Domain Names ” means any domain names registered in the name of Lorimer Patrick Tucker and incorporating or confusingly similar to an Owned Intellectual Property or otherwise used or held for use in connection with the Business including, without limitation, those domain names listed in Schedule 13;

“ Tucker Patent Deed of Assignment ” means the patent deed of assignment between Lorimer Patrick Tucker and Aon Capital Markets Limited, in the agreed form;

“ TUPE ” shall mean the Transfer of Undertakings (Protection of Employment) Regulations 2006 as amended from time to time;

“ TULRCA ” means the Trade Union Labour Relations (Consolidation) Act 1992 (as amended from time to time);

“ UK Aggregate Seller Revenue ” means the aggregate seller revenue calculated pursuant to paragraph 4 of Schedule 2 to this Agreement;

“ UK Contingent Purchase Price ” means the contingent purchase price payable by the Buyer to the Seller computed in accordance with and subject to each of the conditions of Schedule 2 of this Agreement;

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“ Underwriters ” means the reinsurance providers that underwrite the Programmes;

“ US Aggregate Seller Revenue ” means the aggregate seller revenue calculated pursuant to paragraph 3 of Exhibit A to the US APA;

“ US APA ” means the Asset Purchase Agreement for the acquisition of certain assets of Gallagher Re, Inc. by Aon Re, Inc. dated as of February 22, 2008;

“ US Contingent Purchase Price ” means the contingent purchase price payable under the US APA, as calculated in accordance with the provisions of Exhibit A thereto;

“ VAT ” and “ Value Added Tax ” means value added tax as imposed by the VAT Act and any other tax of a similar fiscal nature whether imposed in the United Kingdom (instead of or in addition to value added tax) or elsewhere from time to time;

“ VAT Act ” means the Value Added Tax Act 1994 as modified or re-enacted or both from time to time whether before or after the date of this Agreement and any subordinate legislation made under it from time to time whether before or after the date of this Agreement;

“ Warranty ” means a Buyer Warranty or a Seller Warranty, and “ warranties ” means all Buyer warranties and Seller warranties; and

“ Warranty Claim ” means a claim by the Buyer under the Seller Warranties.

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In this clause 9, “ Liabilities ” means in respect of any matter, event or circumstances all payments, losses, liabilities, damages, costs and expenses (including but not limited to reasonable legal and other professional fees and disbursements and the costs of investigation, litigation, settlement, judgement, interest and penalties) incurred by a party and “Liability” shall be construed accordingly.