Fourth Supplemental Indenture

Exhibit 4.1

WILLIS NORTH AMERICA INC.,

Issuer

WILLIS GROUP HOLDINGS LIMITED

WILLIS INVESTMENT UK HOLDINGS LIMITED

TA I LIMITED

TA II LIMITED

TA III LIMITED

TRINITY ACQUISITION PLC

TA IV LIMITED

WILLIS GROUP LIMITED,

Guarantors

and

THE BANK OF NEW YORK MELLON
(as successor to JPMORGAN CHASE BANK, N.A.)

Trustee

Fourth Supplemental Indenture

Dated as of September 29, 2009

to the Indenture dated as of July 1, 2005

Creating one series of Securities designated

7.0% Senior Notes Due 2019

TABLE OF CONTENTS

          FOURTH SUPPLEMENTAL INDENTURE, dated as of September 29, 2009, between WILLIS NORTH AMERICA INC., a Delaware corporation (the “ Issuer ”), WILLIS GROUP HOLDINGS LIMITED, a company organized and existing under the laws of Bermuda (the “ Parent Guarantor ”), TA I LIMITED, a company organized and existing under the laws of England and Wales, TA II LIMITED, a company organized and existing under the laws of England and Wales, TA III LIMITED, a company organized and existing under the laws of England and Wales, TRINITY ACQUISITION PLC, a company organized and existing under the laws of England and Wales, TA IV LIMITED, a company organized and existing under the laws of England and Wales, and WILLIS GROUP LIMITED, a company organized and existing under the laws of England and Wales (collectively, including the Parent Guarantor, the “ Original Guarantors ”) and WILLIS INVESTMENT UK HOLDINGS LIMITED, a company organized and existing under the laws of England and Wales (together with the Original Guarantors, the “ Guarantors ”) and THE BANK OF NEW YORK MELLON (formerly known as THE BANK OF NEW YORK) (as successor to JPMORGAN CHASE BANK, N.A.), a New York banking corporation, as trustee (the “ Trustee ”).

RECITALS OF THE ISSUER AND THE GUARANTORS

          WHEREAS, the Issuer and the Original Guarantors have heretofore executed and delivered to the Trustee an Indenture, dated as of July 1, 2005 (the “ Original Indenture ” ), as supplemented by the First Supplemental Indenture dated July 1, 2005, (the “ First Supplemental Indenture ”), the Second Supplemental Indenture dated as of March 28, 2007, (the “ Second Supplemental Indenture ”) and the Third Supplemental Indenture dated as of October 1, 2008 (entered into between the Issuer, the Guarantors and the Trustee) (the “ Third Supplemental Indenture ” and together with the Original Indenture, the First Supplemental Indenture and the Second Supplemental Indenture, the “ Existing Indenture ” ) providing for the issuance from time to time of its unsecured senior debentures, notes or other evidences of Indebtedness (the “ Securities ” ), to be issued in one or more series as provided in the Original Indenture;

          WHEREAS, Section 10.01 of the Original Indenture provides that the Issuer, each Guarantor and the Trustee may from time to time enter into one or more indentures supplemental thereto to establish a new series of Securities and add certain provisions to the Original Indenture;

          WHEREAS, Section 3.01 of the Original Indenture provides that the Issuer may enter into one or more indentures supplemental thereto to establish the form and terms of a series of Securities issued pursuant to the Original Indenture;

          WHEREAS, the Issuer, pursuant to the foregoing authority, proposes in and by this Fourth Supplemental Indenture (the “ Supplemental Indenture ” and, together with the Original Indenture, the “ Indenture ” ) to supplement the Original Indenture insofar as it will apply only to the one series of securities to be known as the Issuer’s

“7.0% Senior Notes due 2019” (the “ Notes ” ) issued hereunder (and not to any other series);

          WHEREAS, the Issuer and the Guarantors have duly authorized the execution and delivery of this Supplemental Indenture; and

          WHEREAS, all things necessary have been done to make this Supplemental Indenture a valid agreement of the Issuer and the Guarantors, in accordance with its terms and the terms of the Original Indenture.

          NOW, THEREFORE, for and in consideration of the premises and the covenants and agreements contained herein, and for other good and valuable consideration the receipt of which is hereby acknowledged, the parties hereto agree as follows:

ARTICLE I

7.0% Senior Notes due 2019

          SECTION 1.01. Creation of Series; Establishment of Form .

     7.0% Senior Notes due 2019

          (1) There is hereby established a new series of Securities under the Indenture entitled “7.0% Senior Notes due 2019”.

          (2) The form of the Notes, including the form of the certificate of authentication, is attached hereto as Exhibit A.

          (3) The Trustee shall authenticate and deliver the Notes for original issue in an aggregate principal amount of $300,000,000 upon an Issuer Order for the authentication and delivery of the Notes. The Issuer may from time to time issue additional Notes in accordance with Sections 3.01 and 10.01 of the Original Indenture. Any additional Notes subsequently issued shall not be limited by the aggregate principal amount of this Supplemental Indenture. The Notes issued originally hereunder, together with any additional Notes subsequently issued, shall be treated as a single series for purposes of the Indenture.

          (4) The Notes shall be issued in registered form without coupons.

          (5) The Notes shall not have a sinking fund.

          (6) The principal of the Notes shall be due on September 29, 2019.

          (7) Subject to Section 1.07 of this Supplemental Indenture, the outstanding principal amount of the Notes shall bear interest at the rate of 7.0% per annum, from September 29, 2009 or from the most recent Interest Payment Date (as

defined below) to which interest has been paid or duly provided for, as the case may be, payable semi-annually in arrears on March 15 and September 15 (each, an “ Interest Payment Date ”), commencing on March 15, 2010, to the Persons in whose names the Notes are registered at the close of business on the Regular Record Date (as defined in Section 1.02) for such interest and at the Stated Maturity of the Notes, until the principal thereof is paid or made available for payment. Interest on the Notes will be computed on the basis of a 360-day year comprised of twelve 30-day months. Any such interest due on an Interest Payment Date that is not so punctually paid or duly provided for shall forthwith cease to be payable to the Holders on such Regular Record Date and may either be paid to the Person or Persons in whose name the Notes are registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee ( “ Special Record Date ” ), notice whereof shall be given to Holders of the Notes not less than ten (10) days prior to such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange, if any, on which the Notes may be listed, and upon such notice as may be required by any such exchange, all as more fully provided in the Original Indenture.

          (8) The Notes shall be issued in denominations of $2,000 or any integral multiple of $1,000 in excess thereof.

          (9) The Notes due shall be redeemable, in whole at any time or in part from time to time, at the option of the Issuer on any date (a “ Redemption Date ” ), at a Redemption Price equal to the greater of (i) 100% of the principal amount of the Notes to be redeemed and (ii) the sum of the present values of the remaining scheduled payments of principal and interest thereon (exclusive of interest accrued to such Redemption Date) discounted to such Redemption Date on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate plus 50 basis points, plus, in either case, accrued and unpaid interest on the principal amount being redeemed to such Redemption Date.

          SECTION 1.02. Definitions . The following defined terms used herein shall, unless the context otherwise requires, have the meanings specified below. Each capitalized term that is used in this Supplemental Indenture but not defined herein shall have the meaning specified in the Original Indenture.

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

          “ Comparable Treasury Price ” means, with respect to any Redemption Date for the Notes, (1) the average of five Reference Treasury Dealer Quotations for such Redemption Date, after excluding the highest and lowest Reference Treasury Dealer Quotations, or (2) if the Independent Investment Banker obtains fewer than five such Reference Treasury Dealer Quotations, the average of all such quotations.

          “ Depositary ” means The Depository Trust Company or any successor thereto.

          “ Independent Investment Banker ” means one of the Reference Treasury Dealers that the Issuer appoints to act as the Independent Investment Banker from time to time.

          “ Interest Payment Date ” means March 15 and September 15 of each year.

          “ Reference Treasury Dealer ” means (1) each of Banc of America Securities LLC and J.P. Morgan Securities Inc. and their respective successors; provided, however, that if any of the foregoing ceases to be a primary dealer of U.S. government securities in the United States (a “Primary Treasury Dealer”), the Issuer shall substitute another Primary Treasury Dealer and (2) any other Primary Treasury Dealers selected by the Issuer.

          “ Reference Treasury Dealer Quotations ” means, with respect to each Reference Treasury Dealer and any Redemption Date, the average, as determined by the Independent Investment Banker, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Independent Investment Banker by such Reference Treasury Dealer at 5:00 p.m. New York City time on the third (3rd) Business Day preceding such Redemption Date.

          “ Regular Record Date ” means, with respect to each Interest Payment Date, the close of business on the respective March 1 and September 1 (whether or not a Business Day) prior to such Interest Payment Date.

          “ Security Register ” means the register, in such office as the Issuer shall keep at the Corporate Trust Office of the Trustee or in any office or agency to be maintained by the Issuer in accordance with Section 3.05 of the Original Indenture, in which the Issuer shall, subject to such reasonable regulations as it may prescribe, provide for the registration of Securities and of registration of transfers of Securities.

          “ Treasury Rate ” means, with respect to any Redemption Date, (a) the yield, under the heading that represents the average for the immediately preceding week, appearing in the most recently published statistical release designated “H.15 (519)” or any successor publication that is published weekly by the Board of Governors of the Federal Reserve System and that establishes yields on actively traded U.S. Treasury securities adjusted to constant maturity under the caption “Treasury Constant Maturities,” for the maturity corresponding to the Comparable Treasury Issue (if no maturity is within three (3) months before or after the remaining term of the Notes, yields for the two published maturities most closely corresponding to the Comparable Treasury Issue will be determined and the Treasury Rate will be interpolated or extrapolated from such yields on a straight line basis, rounding to the nearest month); or (b) if such release (or any successor release) is not published during the week preceding the calculation date or does not contain such yields, the rate per annum equal to the semi-annual equivalent yield to

maturity of the Comparable Treasury Issue, calculated using a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price for such Redemption Date. The Treasury Rate shall be calculated on the third (3rd) Business Day preceding the Redemption Date.

          SECTION 1.03. Payment of Principal and Interest .

          (1) If any Interest Payment Date, Redemption Date or the Stated Maturity of the Notes is not a Business Day, the payment of principal, premium, if any, or interest, as applicable, will be made on the next succeeding Business Day. No interest will accrue on the amount so payable for the period from such Interest Payment Date, Redemption Date or Stated Maturity, as the case may be, to the next succeeding Business Day. “Business Day” means each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on which banking institutions in New York, New York are authorized or obligated by law or executive order to close.

          (2) Payments of principal of, premium, if any, and interest on the Notes represented by a Global Security shall be made by wire transfer of immediately available funds to the Holder of such Global Security; provided, however, that in the case of payments of principal and premium, if any, such Global Security is first surrendered to the Paying Agent. If any of the Notes are no longer represented by a Global Security, (i) payments of principal, premium, if any, and interest due at the Stated Maturity or on a Redemption Date, if any, (except, in the case of interest, where the Redemption Date is an Interest Payment Date) shall be made at the office of the Paying Agent upon surrender of such Notes to the Paying Agent and (ii) payments of interest shall be made, at the option of the Issuer, subject to such surrender where applicable, (A) by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register or (B) by wire transfer at such place and to such account at a banking institution in the United States as may be designated in writing to the Trustee at least sixteen (16) days prior to the date for payment by the Person entitled thereto.

          (3) The Trustee shall initially serve as the Paying Agent with respect to the Notes, with the Place of Payment initially being the Corporate Trust Office.

          SECTION 1.04. Global Securities . The Notes shall initially be issued in the form of one or more Global Securities registered in the name of a nominee of the Depositary. Except under the limited circumstances described below, Notes represented by such Global Security or Global Securities shall not be exchangeable for, and shall not otherwise be issuable as, Notes in definitive form. The Global Securities described above may not be transferred except as a whole by the Depositary to a nominee of the Depositary or by a nominee of the Depositary to the Depositary or another nominee of the Depositary or to a successor Depositary or its nominee or by the Depositary or any such nominee to a successor Depositary or a nominee of such successor Depositary, unless and until the Notes are exchanged in whole or in part for Notes in definitive form.

          Subject to the procedures of the Depositary, a Global Security shall be exchangeable for the Notes registered in the names of Persons other than the Depositary or its nominee only if (i) the Depositary notifies the Trustee and the Issuer that it is no longer willing or able to properly discharge its responsibilities as a Depositary for such Global Security and no qualified successor Depositary shall have been appointed by the Issuer within ninety (90) days of receipt by the Issuer of such notification, or if at any time the Depositary ceases to be a clearing agency registered under the Exchange Act at a time when the Depositary is required to be so registered to act as such Depositary and no qualified successor Depositary shall have been appointed by the Issuer within ninety (90) days after it becomes aware of such cessation, (ii) the Issuer executes and delivers to the Trustee an Issuer Order stating that the Issuer elects to terminate the book-entry system through the Depositary, or (iii) there shall have occurred and be continuing an Event of Default with respect to the Global Security. Any Global Security that is exchangeable pursuant to the preceding sentence shall be exchangeable for the Notes as provided in the Original Indenture.

          SECTION 1.05. Redemption .

          (1) The Issuer shall mail notice of redemption not less than 30 nor more than 60 days prior to the Redemption Date, to each Holder of the Notes to be redeemed. Notwithstanding Section 12.04 of the Original Indenture, the notice of redemption with respect to the foregoing redemption need not set forth the Redemption Price or an estimate thereof, but only the appropriate calculation thereof. The Issuer shall deliver to the Trustee an Officers’ Certificate setting forth the Redemption Price with respect to the foregoing redemption no later than two (2) Business Days prior to the Redemption Date. The Trustee shall have no responsibility for determining said Redemption Price

          (2) On the Redemption Date, and from and after such date (unless the Issuer shall default in the payment of the Redemption Price and accrued interest) such Notes shall cease to bear interest.

          (3) Section 12.03 (Selection by Trustee of Securities to Be Redeemed) of the Original Indenture is hereby amended and restated in its entirety as follows:

     If less than all the 7.0% Senior Notes due 2019 (the “ Notes ”) are to be redeemed, the particular Notes to be redeemed shall be selected not more than 60 days prior to the Redemption Date by the Trustee, from the Outstanding Notes not previously called for redemption, (i) if the Notes are listed on any securities exchange, in accordance with the requirements of such exchange or (ii) if the Notes are not so listed, by any method as the Trustee shall deem fair and appropriate, and which may provide for the selection for redemption of portions (equal to $1,000 or any integral multiple thereof) of the principal amount of Notes of a denomination larger than $2,000; provided, however, that Notes registered in the name of the Issuer shall be excluded from any such selection for redemption

until all Notes not so registered shall have been previously selected for redemption.

     The Trustee shall promptly notify the Issuer in writing of the Notes selected for redemption and, in the case of any Notes selected for partial redemption, the principal amount thereof to be redeemed.

     For all purposes of this Indenture, unless the context otherwise requires, all provisions relating to the redemption of Notes shall relate, in the case of any Notes redeemed or to be redeemed only in part, to the portion of the principal amount of such Notes which has been or is to be redeemed.

          SECTION 1.06. Additional Covenants . The following shall be additional covenants to the covenants set forth in the Original Indenture for the benefit of the Notes only and shall be effective only so long as the Notes are outstanding:

          (1) Limitation on Liens . The Parent Guarantor shall not, and shall not permit any of its Subsidiaries to, directly or indirectly, incur or suffer to exist any Lien, other than a Permitted Lien (an “ Initial Lien ”), securing Indebtedness upon any Capital Stock of any Significant Subsidiary of the Parent Guarantor that is owned, directly or indirectly, by the Parent Guarantor or any of its Subsidiaries, in each case whether owned at the date of the original issuance of the Notes or thereafter acquired, or any interest therein or any income or profits therefrom unless it has made or will make effective provision whereby the Outstanding Notes will be secured by such Lien equally and ratably with (or prior to) all other Indebtedness of the Parent Guarantor or any Subsidiary secured by such Lien. Any Lien created for the benefit of the Holders of the Notes pursuant to the preceding sentence shall provide by its terms that such Lien will be automatically and unconditionally released and discharged upon release and discharge of the Initial Lien.

          “ Permitted Lien ” means a Lien on the Capital Stock of a Significant Subsidiary to secure Indebtedness incurred to finance the purchase price of such Capital Stock; provided that any such Lien may not extend to any other property of the Parent Guarantor or any other Subsidiary of the Parent Guarantor; and provided further that such Indebtedness matures within 180 days from the date such Indebtedness was incurred.

          (2) Limitation on Dispositions of Significant Subsidiaries . The Parent Guarantor shall not, and shall not permit any of its Subsidiaries to, directly or indirectly, sell, transfer or otherwise dispose of, and will not permit any Significant Subsidiary to issue, any Capital Stock of any Significant Subsidiary. Notwithstanding the foregoing limitation, (a) the Parent Guarantor and its Subsidiaries may sell, transfer or otherwise dispose of, and any Significant Subsidiary may issue, any such Capital Stock to any Subsidiary of the Parent Guarantor, (b) any Subsidiary of the Parent Guarantor may sell, transfer or otherwise dispose of, and any Significant Subsidiary may issue, any such securities to the Parent Guarantor or another Subsidiary of the Parent Guarantor, (c) the Parent Guarantor and its Subsidiaries may sell, transfer or otherwise dispose of, and any

Significant Subsidiary may issue, any such Capital Stock if the consideration received is at least equal to the fair market value (as determined by the board of directors of the Parent Guarantor acting in good faith) of such Capital Stock, and (d) the Issuer and its Subsidiaries may sell, transfer or otherwise dispose of, and any Significant Subsidiary may issue, any such securities if required by law or any regulation or order of any governmental or regulatory authority. Notwithstanding the foregoing, the Parent Guarantor may merge or consolidate any of its Significant Subsidiaries into or with another one of its Significant Subsidiaries and may otherwise convey, transfer or lease its properties and assets pursuant to Article NINE of the Original Indenture.

          SECTION 1.07. Interest Rate Adjustment . The interest rate payable on the Notes will be subject to adjustment from time to time if either Moody’s Investors Service, Inc. ( “ Moody’s ” , which term shall include any successor thereto) or Standard & Poor’s Rating Services, a division of McGraw-Hill, Inc. (“ S&P ”, which term shall include any successor thereto an