UNDERWRITING AGREEMENT

Exhibit 1.1

E XECUTION C OPY

UNDERWRITING AGREEMENT

U.S.$2,600,000,000

J.P. MORGAN TRUST AUSTRALIA LIMITED

SERIES 2007-1G WST TRUST

U.S.$ Class A2a Mortgage Backed Floating Rate Notes Due 2038

UNDERWRITING AGREEMENT

May 24, 2007

Barclays Capital Inc.

200 Park Avenue

New York, New York 10166

J.P. Morgan Securities Inc.

270 Park Avenue

New York, New York 10017

HSBC Securities (USA) Inc.

452 Fifth Avenue

New York, New York 10018

as Representatives of the several Underwriters listed in Schedule I

Ladies and Gentlemen:

J.P. Morgan Trust Australia Limited (ABN 49 050 294 052), a limited liability public company under the Corporations Act 2001 of the Commonwealth of Australia in its capacity as trustee of the Series 2007-1G WST Trust (the “Issuer Trustee”) proposes to sell to the several Underwriters listed in Schedule I hereto (the “Underwriters”), for whom you are acting as representative (the “Representatives”), U.S.$2,600,000,000 principal amount of Class A2a Mortgage Backed Floating Rate Notes due 2038 (the “Class A2a Notes” or the “Notes”) issued by the Series 2007-1G WST Trust (the “Trust”). Each Note will be secured by the assets of the Trust. The assets of the Trust include, among other things, a pool of fixed- and variable-rate residential housing loans (the “Housing Loans”) originated or acquired by Westpac Banking Corporation (ABN 33 007 457 141) (“Westpac”) including all monies at any time paid or payable thereon or in respect thereof from, on and after April 10, 2007 (the “Cut-Off Date”) with respect to payments of principal and after May 31, 2007 (the “Closing Date”) with respect to payments of interest, rights under certain insurance policies with respect to the Housing Loans,

the collection account relating to the Trust and the rights of the Issuer Trustee under the Master Trust Deed, the Series Notice, the Servicing Agreement, the Notes, the Security Trust Deed, the Note Trust Deed, the Swap Agreements and the Agency Agreement, each as defined below (the “Basic Documents”). The Trust will be created pursuant to the Master Trust Deed, dated February 14, 1997 (the “Master Trust Deed”) between the Issuer Trustee and The Mortgage Company Pty Limited (ABN 86 070 968 302) and a series notice, to be dated on or about May 29, 2007 (the “Series Notice”), between the Issuer Trustee and Westpac Securitisation Management Pty Limited (ABN 73 081 709 211) (the “Trust Manager”), which sets forth specific provisions regarding the Trust and details the provisions of the Notes. The Note Trust Deed, to be dated on or about May 29, 2007 (the “Note Trust Deed”) by and among the Issuer Trustee, the Trust Manager and The Bank of New York (the “Note Trustee”) will provide for the issuance and registration of the Notes in accordance with the terms and conditions attached thereto. Westpac will act as servicer (the “Servicer”) of the Housing Loans. The Trust Manager and Westpac (except in its capacity as Servicer) are each a “Westpac Party” and collectively are referred to herein as the “Westpac Parties.” The Notes are described in the Prospectus (as defined below) which the Trust Manager has furnished to the Underwriters.

In addition, the following terms shall have the following meanings:

(i) “ABS Informational and Computational Materials” shall have the meaning given such term in Item 1101 of Regulation AB.

(ii) “Approved Offering Materials” means the Preliminary Prospectus and any Issuer Free Writing Prospectus that Westpac or the Trust Manager identifies in writing to the Underwriters as “Approved Offering Materials.”

(iii) “Contract of Sale” has the same meaning as in Rule 159 of the Securities Act Regulations and all SEC guidance relating to Rule 159.

(iv) “Free Writing Prospectus” shall have the meaning given such term in Rules 405 and 433 of the Securities Act Regulations.

(v) “Issuer Free Writing Prospectus” shall have the meaning given such term in Rule 433 of the Securities Act Regulations.

(vi) “Issuer Information” shall mean any “issuer information” as defined in Rule 433(h) of the Securities Act Regulations and footnote 271 of SEC Release No. 33-8591 (Securities Offering Reform) and identified by the Trust Manager as Issuer Information and relating to the Notes or the offering thereof.

(vii) “Permitted Additional Materials” shall mean information that is not ABS Informational and Computational Materials and (x) that are referred to in Section 5(a)(vii)(C) so long as any Issuer Information provided by any Underwriter pursuant to Section 5(a)(vii)(C) is limited to information included within the definition of ABS Informational and Computational Materials, (y) that constitute Note price, yield, weighted average life, subscription or allocation information, or a trade confirmation, or (z) otherwise with respect to which the Trust Manager has provided written consent to any Underwriter to include in a Free Writing Prospectus.

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(viii) “Pool Information” means the information furnished by magnetic tape, diskette or any other computer readable format, or in writing to the Underwriter by Westpac or the Trust Manager regarding the Mortgage Loans.

(ix) “Underwriter Derived Information” shall refer to information of the type described in clause (5) of footnote 271 of SEC Release No. 33-8591 (Securities Offering Reform) when prepared by the Underwriters, including traditional computational and analytical materials prepared by the Underwriters.

(x) “Underwriter Free Writing Prospectus” shall mean all Free Writing Prospectuses prepared by or on behalf of the Underwriters other than any Underwriter Prepared Issuer FWP, including any Permitted Additional Materials.

(xi) “Underwriter Prepared Issuer FWP” shall mean any Free Writing Prospectus prepared by or on behalf of any Underwriter that contains any Issuer Information, including any Free Writing Prospectus or portion thereof prepared by or on behalf of any Underwriter that contains only a description of the final terms of the Notes or of the offering of the Notes.

(xii) “Written Communication” shall have the meaning given such term in Rule 405 of the Securities Act Regulations.

To the extent not defined herein, capitalized terms used herein have the meanings assigned to such terms in the Series Notice and the Master Trust Deed.

In this Agreement, a reference to the Issuer Trustee is a reference to the Issuer Trustee in its capacity as trustee of the Trust only, and in no other capacity. Any reference to the assets, business, property or undertaking of the Issuer Trustee is a reference to the Issuer Trustee in that capacity only.

The Westpac Parties and the Issuer Trustee hereby agree with the Underwriters as follows:

The Westpac Parties and the Issuer Trustee understand that the Underwriters intend (i) to make a public offering of their respective portions of the Notes as soon after the parties hereto have executed and delivered this Agreement as in the judgment of the Representatives is advisable and (ii) initially to offer the Notes upon the terms set forth in the Prospectus, and in compliance with all applicable laws and regulations.

(a) Subject to the terms and conditions and in reliance upon the representations and warranties set forth herein, the Issuer Trustee, at the direction of the Trust Manager, agrees to

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sell the Notes to the several Underwriters as hereinafter provided, and each Underwriter agrees to purchase, severally and not jointly, from the Issuer Trustee the respective principal amount of Notes set forth opposite such Underwriter’s name in Schedule I hereto at a price equal to 100 percent of the principal amount of each Note.

(b) Westpac shall pay A$1,585,366.00 (the “Commission”) to the Underwriters on the Closing Date in immediately available funds by official bank check or checks or wire transfer to a bank account or accounts directed by the Representatives.

Payment for the Notes shall be made by wire transfer in immediately available funds to the account specified by the Issuer Trustee to the Representatives no later than noon, New York City time, on the Closing Date, or at such other time on the same or such other date, not later than the fifth Business Day thereafter, as the Representatives and the Trust Manager may agree upon in writing.

Payment for the Notes shall be made against delivery to the nominee of The Depository Trust Company (“DTC”) for the account of the Representatives of one or more book-entry notes (the “Book-Entry Notes”) representing the Notes, with any transfer taxes payable in connection with the transfer to the Underwriters of the Notes duly paid by the Issuer Trustee. The Book-Entry Notes will be made available for inspection by the Representatives at the office of Mayer, Brown Rowe & Maw LLP, 1675 Broadway, New York, New York 10019 not later than 1:00 P.M., New York City time, on the Business Day prior to the Closing Date. As used herein the term “Business Day” means any day other than a day on which banks are permitted or required to be closed in New York City.

(a) The Issuer Trustee represents and warrants to each Underwriter that as at the date hereof and as of the Closing Date:

(i) since the respective dates as of which information is provided in the Preliminary Prospectus and the Prospectus, there has been no material adverse change in the condition (financial or otherwise) of the Issuer Trustee which is material in the context of the Issuer Trustee performing its obligations and duties under the Notes and each Basic Document to which it is or is to be a party;

(ii) the Issuer Trustee is a corporation duly incorporated and existing under the laws of the Commonwealth of Australia; it is lawfully qualified and holds all Authorisations (as defined in the Master Trust Deed) necessary to carry on its business as described in the Prospectus and to issue the Notes and to act as required by each Basic Document to which it is or is to be a party and by law to comply with the requirements of any legislation and subordinate legislation (including, without limitation and to the extent relevant, any Consumer Credit Legislation (as defined in the Master Trust Deed)) and no other thing is required to be done (including without limitation the making of any filing or registration) in order to issue the Notes or to execute and act as required by each Basic Document to which it is to be a party;

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(iii) this Agreement has been duly authorized, executed and delivered by the Issuer Trustee. The Note Trust Deed will have been duly qualified under the Trust Indenture Act of 1939 as of the Closing Date;

(iv) the Notes have been duly authorized, and, when issued, delivered and paid for pursuant to this Agreement, will have been duly executed, authenticated, issued and delivered and will constitute valid and binding obligations of the Issuer Trustee, entitled to the benefits provided by the Note Trust Deed and the Security Trust Deed, subject to general principles affecting creditors’ rights and general principles of equity. Each Basic Document to which the Issuer Trustee is a party has been duly authorized by the Issuer Trustee, and, when executed and delivered by the Issuer Trustee and, each of the other parties thereto, each Basic Document to which it is a party will constitute a legal, valid and binding obligation of the Issuer Trustee, enforceable against the Issuer Trustee in accordance with its terms, subject as to enforceability to applicable bankruptcy, insolvency, reorganization, conservatorship, receivership, liquidation or other similar laws affecting the enforcement of creditors’ rights generally and to general equitable principles;

(v) the Issuer Trustee is not, nor with the giving of notice or lapse of time or both would be, in violation of or in default under, its Constitution or any indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which the Issuer Trustee is a party or by which it or any of its properties is bound, except for violations and defaults which individually and in the aggregate would not have a material adverse effect on the transactions contemplated herein or in the Basic Documents; the issue and sale of the Notes and the performance by the Issuer Trustee of all of the provisions of its obligations under the Notes, the Basic Documents to which it is a party and this Agreement and the consummation of the transactions herein and therein contemplated will not conflict with or result in a breach of any of the terms or provisions of, or constitute a default under, any material indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which the Issuer Trustee is a party or by which the Issuer Trustee is bound or to which any of the property or assets of the Trust is subject, nor will any such action result in any violation of the provisions of the Constitution of the Issuer Trustee or any applicable law or statute or any order, rule or regulation of any court or governmental agency or body having jurisdiction over the Issuer Trustee, or any of its properties; or result in the creation or imposition of any lien or encumbrance upon any of its property pursuant to the terms of any indenture, mortgage, contract or other instrument other than pursuant to the Basic Documents; and, to the knowledge of the Issuer Trustee, no consent, approval, authorization, order, license, registration or qualification of or with any such court or governmental agency or body is required for the issue and sale of the Notes or the consummation by the Issuer Trustee of the transactions contemplated by this Agreement or the Basic Documents, except such consents, approvals, authorizations, orders, licenses, registrations or qualifications as have been obtained, or will be obtained as of the Closing Date, under the Securities Act, the Trust Indenture Act and as may be required under state securities or “Blue Sky” laws in connection with the purchase and distribution of the Notes by the Underwriters;

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(vi) other than as set forth or contemplated in the Preliminary Prospectus and the Prospectus, there are no legal or governmental investigations, actions, suits or proceedings pending or, to the knowledge of the Issuer Trustee, threatened against or affecting the Issuer Trustee or the Trust or, to which the Issuer Trustee is or may be a party or to which the Issuer Trustee or any property of the Trust is or may be the subject, (a) asserting the invalidity of this Agreement or of any of the Basic Documents in relation to the Issuer Trustee, (b) seeking to prevent the issuance of the Notes or the consummation of any of the transactions contemplated by this Agreement or any of the Basic Documents by the Issuer Trustee, (c) that may adversely affect the U.S. federal or Australian federal or state income, excise, franchise or similar tax attributes of the Notes, (d) that could materially and adversely affect the performance of the Issuer Trustee of its obligations under, or the validity or enforceability of, this Agreement or any of the Basic Documents by the Issuer Trustee or (e) which could individually or in the aggregate reasonably be expected to have a material adverse effect on the interests of the holders of the Notes or the marketability of the Notes;

(vii) the representations and warranties of the Issuer Trustee contained in the Basic Documents to which it is a party are true and correct in all material respects as of the date when made;

(viii) PricewaterhouseCoopers LLP are independent public accountants with respect to the Issuer Trustee within the meaning of the Securities Act;

(ix) to the Issuer Trustee’s knowledge, no event has occurred which would entitle the Trust Manager to direct the Issuer Trustee to retire as trustee of the Trust under clause 24 of the Master Trust Deed;

(x) the Issuer Trustee has not taken any corporate action nor (to the best of its knowledge and belief) have any other steps been taken or legal proceedings been started or threatened against the Issuer Trustee for its winding-up, dissolution or reorganization or for the appointment of a receiver, receiver and manager, administrator, provisional liquidator or similar officer of it or of any or all of its assets;

(xi) subject to compliance with Section 128F of the Income Tax Assessment Act 1936 of Australia (the “Tax Act”) and compliance by the Underwriters with clause 11(a), the paragraph following such clause, clause 11(b) and clause 11(c) hereto, no stamp or other duty is assessable or payable in, and no withholding or deduction for any taxes, duties, assessments or governmental charges of whatever nature is imposed or made for or on account of any income, registration, transfer or turnover taxes, customs or other duties or taxes of any kind, levied, collected, withheld or assessed by or within, the Commonwealth of Australia or any sub-division of or authority therein or thereof having power to tax in such jurisdiction, in connection with the authorization, execution or delivery of the agreements to which it is to be a party or with the authorization, execution, issue, sale or delivery of the Notes and the performance of the Issuer Trustee’s obligations under the agreements to which it is to be a party and the Notes;

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(xii) the Notes and the obligations of the Issuer Trustee under the Note Trust Deed will be secured (pursuant to the Security Trust Deed) by a first-ranking floating charge over the assets of the Trust; and

(xiii) no event has occurred or circumstances arisen which, had the Notes already been issued, would (whether or not with the giving of notice and/or the passage of time and/or the fulfillment of any other requirement) constitute an Event of Default under the Security Trust Deed.

(b) The Trust Manager represents and warrants to each Underwriter and the Issuer Trustee as at the date hereof and as of the Closing Date that:

(i) a Registration Statement for the registration of Mortgage Backed Notes (issuable in series), including the Notes, on Form S-3 (No. 333-140399) has (a) been prepared by the Trust Manager in conformity with the requirements of the United States Securities Act of 1933, as amended (the “Securities Act”) and the rules and regulations (the “Rules and Regulations”) of the United States Securities and Exchange Commission (the “SEC”) thereunder, (b) been filed with the SEC under the Securities Act and (c) become effective under the Securities Act. Copies of such Registration Statement have been delivered by the Trust Manager to the Underwriters. As used in this Agreement, “Effective Time” means the date and the time as of which such Registration Statement, or the most recent post-effective amendment thereto, if any, was declared effective by the SEC; “Effective Date” means the date of the Effective Time; “Registration Statement” means such registration statement as amended, at the Effective Time and as of the Closing Date, including any documents incorporated by reference therein at such time, or if any post-effective amendment has been filed with respect thereto, as amended by the most recent post-effective amendment at the time of its effectiveness; “Base Prospectus” means the form of base prospectus included in the Registration Statement as most recently filed with the SEC; and “Prospectus Supplement” means the form of the prospectus which includes the Base Prospectus and a prospectus supplement describing the Notes and the offering thereof; and “Prospectus” means such final prospectus dated May 24, 2007 as first supplemented by a prospectus supplement, relating to the Notes, as first filed with the SEC pursuant to paragraph (1), (2), (3), (4) or (5) of Rule 424(b) of the Rules and Regulations. Any preliminary form of the Prospectus Supplement to be filed pursuant to Rule 424(b) is referred to as a “Preliminary Prospectus Supplement” and, together with the Base Prospectus, and as amended or supplemented if the Trust Manager shall have furnished any amendments or supplements thereto, a “Preliminary Prospectus.” Reference made herein to the Prospectus shall be deemed to refer to and include any documents incorporated by reference therein pursuant to Item 12 of Form S-3 under the Securities Act, as of the date of the Prospectus, and any reference to any amendment or supplement to the prospectus shall be deemed to refer to and include any document filed under the United States Securities Exchange Act of 1934 (the “Exchange Act”) after the date of the Prospectus and incorporated by reference in the Prospectus, and any reference to any amendment or supplement to the Registration Statement shall be deemed to include any report filed with the SEC with respect to the Trust Manager pursuant to Section 13(a) or 15(d) of the Exchange Act after the date of the Prospectus that is incorporated by reference in the Registration Statement. There are no contracts or

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documents of the Trust Manager which are required to be filed as exhibits to the Registration Statement pursuant to the Securities Act or the Rules and Regulations which have not been so filed or incorporated by reference therein on or prior to the Effective Date of the Registration Statement. As interpreted by the SEC, the conditions for use of Form S-3 as set forth in the General Instructions thereto have been satisfied;

(ii) no stop order suspending the effectiveness of the Registration Statement has been issued and no proceeding for that purpose has been instituted or, to the knowledge of the Trust Manager, threatened by the SEC; and the Registration Statement and Prospectus (as amended or supplemented if the Trust Manager shall have furnished any amendments or supplements thereto) comply, or will comply, as the case may be, in all material respects with the Securities Act and the United States Trust Indenture Act of 1939, as amended, and the rules and regulations of the SEC thereunder (collectively, the “Trust Indenture Act”) and do not and will not, as of the Effective Date as to the Registration Statement and any amendment thereto and as of the date of the Prospectus and any amendment or supplement thereto, contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading, and the Prospectus, as amended or supplemented, at the Closing Date will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading; except that the foregoing representations and warranties shall not apply to: (a) that part of the Registration Statement which constitutes the Statement of Eligibility and Qualification (Form T-1) of the Note Trustee under the Trust Indenture Act; (b) statements or omissions in the Registration Statement or the Prospectus made in reliance upon and in conformity with information relating to any Underwriter furnished to the Trust Manager in writing by such Underwriter through the Representatives expressly for use therein; (c) information (except as to any information or materials provided by a Westpac Party to produce such information) under the heading “Prepayment and Yield Considerations” in the Prospectus;

(iii) the documents incorporated by reference in the Prospectus, when they became effective or were filed with the SEC, as the case may be, conformed in all material respects to the requirements of the Securities Act or the Exchange Act, as applicable, and the Rules and Regulations of the SEC thereunder, and none of such documents contained an untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading; and any further documents so filed and incorporated by reference in the Prospectus, when such documents become effective or are filed with the SEC, as the case may be, will conform in all material respects to the requirements of the Securities Act or the Exchange Act, as applicable, and the Rules and Regulations of the SEC thereunder and will not contain 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; provided that no representation or warranty is made as to information contained in or omitted from the Registration Statement or the Prospectus in reliance upon and in conformity with information furnished to the Trust Manager in writing by the Underwriters expressly for use therein;

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(iv) since the respective dates as of which information is provided in the Registration Statement, the Preliminary Prospectus and the Prospectus, there has not been any material adverse change, or any development involving a prospective material adverse change, in or affecting the condition (financial or otherwise) or in or affecting the earnings, business or operations of the Trust Manager, taken as a whole, in each case, whether or not arising in the ordinary course of business, otherwise than as set forth or contemplated in the Prospectus, as supplemented or amended as of the Closing Date;

(v) each Issuer Free Writing Prospectus (as of its date) did not, and the Approved Offering Materials as of the date of the Approved Offering Materials did not and as of the date of the first Contract of Sale will not and as of the Closing Date will not, include an untrue statement or 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;

(vi) the Trust Manager was not, as of any date on or after which a bona fide offer (as used in Rule 164(h)(2) of the Securities Act Regulations) of the Notes was made, an Ineligible Issuer, as such term is defined in Rule 405 of the Securities Act Regulations;

(vii) the Trust Manager is a corporation duly incorporated and validly existing under the Corporations Act 2001 of the Commonwealth of Australia, the Trust Manager has the power and authority (corporate and other) to own its properties and conduct its business as described in the Prospectus and to enter into and perform its obligations under this Agreement and the Basic Documents to which it is or is to be a party and carry out the transactions contemplated by such Basic Documents; the Trust Manager has been duly qualified or licensed for the transaction of business and is in good standing under the laws of each other jurisdiction in which it owns or leases properties, or conducts any business, so as to require such qualification or licensing, other than where the failure to be so qualified or licensed or in good standing would not have a material adverse effect on the transactions contemplated herein or in the Basic Documents;

(viii) this Agreement has been duly authorized, executed and delivered by the Trust Manager;

(ix) each of the Basic Documents to which it is a party has been duly authorized by the Trust Manager, and, when executed and delivered by the Trust Manager and each of the other parties thereto, each of the Basic Documents to which it is a party will constitute a legal, valid and binding obligation of the Trust Manager, enforceable against the Trust Manager in accordance with its terms, subject as to enforceability to applicable bankruptcy, insolvency, reorganization, conservatorship, receivership, liquidation or other similar laws affecting the enforcement of creditors rights generally and to general equitable principles;

(x) the Notes and the Basic Documents each will conform to the descriptions thereof in the Prospectus;

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(xi) the Trust Manager is not, nor with the giving of notice or lapse of time or both would be, in violation of or in default under, its Constitution or any indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which it is a party or by which it or any of its properties is bound, except for violations and defaults which individually and in the aggregate would not have a material adverse effect on the transactions contemplated herein or in the Basic Documents; the performance by the Trust Manager of all of the provisions of its obligations under the Basic Documents to which it is a party and this Agreement and the consummation of the transactions herein and therein contemplated will not conflict with or result in a breach of any of the terms or provisions of, or constitute a default under, any material indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which the Trust Manager is a party or by which the Trust Manager is bound or to which any of the property or assets of the Trust Manager is subject, nor will any such action result in any violation of the provisions of the Constitution of the Trust Manager or any applicable law or statute or any order, rule or regulation of any court or governmental agency or body having jurisdiction over the Trust Manager, or any of its properties; or result in the creation or imposition of any lien or encumbrance upon any of its property pursuant to the terms of any indenture, mortgage, contract or other instrument other than pursuant to the Basic Documents; and no consent, approval, authorization, order, license, registration or qualification of or with any such court or governmental agency or body is required for the issue and sale of the Notes or the consummation by the Trust Manager of the transactions contemplated by this Agreement or the Basic Documents, except such consents, approvals, authorizations, orders, licenses, registrations or qualifications as have been obtained, or will be obtained as of the Closing Date, under the Securities Act, the Trust Indenture Act and as may be required under state securities or “Blue Sky” laws in connection with the purchase and distribution of the Notes by the Underwriters;

(xii) other than as set forth or contemplated in the Preliminary Prospectus and the Prospectus, there are no legal or governmental investigations, actions, suits or proceedings pending or, to the knowledge of the Trust Manager, threatened against or affecting the Trust Manager or its properties or, to which the Trust Manager is or may be a party or to which the Trust Manager or any property of the Trust Manager is or may be the subject, (a) asserting the invalidity of this Agreement or of any of the Basic Documents in relation to the Trust Manager, (b) seeking to prevent the issuance of the Notes or the consummation of any of the transactions contemplated by this Agreement or any of the Basic Documents, (c) that may adversely affect the U.S. federal or Australian federal or state income, excise, franchise or similar tax attributes of the Notes, (d) that could materially and adversely affect the performance of the Trust Manager of its obligations under, or the validity or enforceability of, this Agreement or any of the Basic Documents by the Trust Manager, or (e) which could individually or in the aggregate reasonably be expected to have a material adverse effect on the interests of the holders of the Notes or the marketability of the Notes; and there are no statutes, regulations, contracts or other documents that are required to be filed as an exhibit to the Registration Statement or required to be described in the Registration Statement or the Prospectus which are not filed as required;

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(xiii) the representations and warranties of the Trust Manager contained in the Basic Documents to which it is a party are true and correct in all material respects as of the date when made;

(xiv) PricewaterhouseCoopers LLP are independent public accountants with respect to the Trust Manager within the meaning of the Securities Act;

(xv) the Trust Manager owns, possesses or has obtained all Authorisations (as defined in the Master Trust Deed), licenses, permits, certificates, consents, orders, approvals and other authorizations from, and has made all declarations and filings with, all federal, state, local and other governmental authorities (including foreign regulatory agencies), all self-regulatory organizations and all courts and other tribunals, domestic or foreign, necessary to perform its obligations under this Agreement and the Basic Documents, and the Trust Manager has not received any actual notice of any proceeding relating to revocation or modification of any such Authorisation, license, permit, certificate, consent, order, approval or other authorization; and the Trust Manager is in compliance with all laws and regulations necessary for the performance of its obligations under this Agreement and the Basic Documents;

(xvi) to the knowledge of the Trust Manager, no event has occurred which would entitle the Trust Manager to direct the Issuer Trustee to retire as trustee of the Trust under clause 24 of the Master Trust Deed;

(xvii) the Trust Manager has not taken any corporate action nor (to the best of its knowledge and belief) have any other steps been taken or legal proceedings been started or threatened against the Trust Manager for its winding-up, dissolution or reorganization or for the appointment of a receiver, receiver and manager, administrator, provisional liquidator or similar officer of it or of any or all of its assets;

(xviii) subject to compliance with Section 128F of Tax Act and compliance by the Underwriters with clause 11 of this Agreement, no stamp or other duty is assessable or payable in, and no withholding or deduction for any taxes, duties, assessments or governmental charges of whatever nature is imposed or made for or on account of any income, registration, transfer or turnover taxes, customs or other duties or taxes of any kind, levied, collected, withheld or assessed by or within, the Commonwealth of Australia or any sub-division of or authority therein or thereof having power to tax in such jurisdiction, in connection with the authorization, execution or delivery of the agreements to which it is to be a party or with the authorization, execution, issue, sale or delivery of the Notes and the performance of the Trust Manager’s obligations under the agreements to which it is to be a party and the Notes; and

(xix) no event has occurred or circumstances arisen which, had the Notes already been issued, would (whether or not with the giving of notice and/or the passage of time and/or the fulfillment of any other requirement) constitute an Event of Default under the Security Trust Deed.

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(c) Westpac represents and warrants to each Underwriter and the Issuer Trustee as at the date hereof and the Closing Date that:

(i) Westpac is a corporation organized under the laws of New South Wales, Australia;

(ii) this Agreement has been duly authorized, executed and delivered by Westpac;

(iii) the representations and warranties of Westpac contained in the Basic Documents are true and correct in all material respects as of the date when made;

(iv) since the respective dates as of which information is provided in the Registration Statement, the Preliminary Prospectus and the Prospectus there has been no material adverse change in the condition (financial or otherwise) or earnings of Westpac or the Westpac Group; and

(v) as of the Closing Date, Westpac will have transferred to the Issuer Trustee a valid equitable assignment of each related Housing Loan offered for sale by it to the Issuer Trustee.

(a) Each Underwriter, severally and not jointly, and solely as to itself, represents and warrants to and agrees with the Trust Manager, Westpac and the Issuer Trustee that as of the date hereof and as of the Closing Date, as follows:

(i) Such Underwriter has complied with all of its obligations hereunder, including, without limitation, Section 11;

(ii) with respect to all Underwriter Prepared Issuer FWP and Underwriter Free Writing Prospectuses, if any, such Underwriter Prepared Issuer FWP and Underwriter Free Writing Prospectuses are accurate in all material respects (taking into account the assumptions explicitly set forth in such Underwriter Prepared Issuer FWP and Underwriter Free Writing Prospectuses), except that such Underwriter makes no representation to the extent that any misstatements or omissions were the result of any inaccurate Issuer Information (including but not limited to Pool Information) supplied by the Issuer Trustee or Westpac Parties to such Underwriter;

(iii) Prior to the Closing Date each Underwriter shall notify the Trust Manager or Westpac of the earlier of (x) the date on which the Preliminary Prospectus is first used and (y) the time of the first Contract of Sale to which such Preliminary Prospectus relates;

(iv) Prior to the date of the first Contract of Sale made based on the Approved Offering Materials, each Underwriter represents, warrants and agrees that it has not pledged, sold, disposed of or otherwise transferred any Note, Mortgage Loans or any interest in any Note;

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(v) It is understood that the Underwriters will solicit offers to purchase the Notes as follows:

A. Prior to the time that the Underwriters have received the Approved Offering Materials they may, in compliance with the provisions of this Agreement, solicit offers to purchase Notes; provided, that they shall not accept any such offer to purchase a Note or any interest in any Note or Mortgage Loan or otherwise enter into any Contract of Sale for any Note, any interest in any Note or any Mortgage Loan prior to their conveyance of Approved Offering Materials to the investor.

B. Any Written Communication relating to the Notes made by an Underwriter in compliance with the terms of this Agreement prior to the time such Underwriter has entered into a Contract of Sale for Notes with the recipient shall prominently set forth the following statements (or a substantially similar statements approved by the Trust Manager).

The information in this free writing prospectus, if conveyed prior to the time of your contractual commitment to purchase any of the Notes, supersedes any information contained in any prior similar materials relating to the Notes. The information in this free writing prospectus is preliminary, and is subject to completion or change. This free writing prospectus is being delivered to you solely to provide you with information about the offering of the Notes referred to in this free writing prospectus and to solicit an offer to purchase the Notes, when, as and if issued. Any such offer to purchase made by you will not be accepted and will not constitute a contractual commitment by you to purchase any of the Notes, until we have accepted your offer to purchase Notes.

The Notes referred to in these materials are being sold when, as and if issued. The issuer is not obligated to issue such Notes or any similar security and the underwriter’s obligation to deliver such Notes is subject to the terms and conditions of the underwriting agreement and the availability of such Notes when, as and if issued. You are advised that the terms of the Notes, and the characteristics of the mortgage loan pool backing them, may change (due, among other things, to the possibility that mortgage loans that comprise the pool may become delinquent or defaulted or may be removed or replaced and that similar or different mortgage loans may be added to the pool, and that one or more classes of Notes may

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be split, combined or eliminated), at any time prior to issuance or availability of a final prospectus. You are advised that Notes may not be issued that have the characteristics described in these materials. The underwriter’s obligation to sell such Notes to you is conditioned on the mortgage loans and Notes having the characteristics described in these materials. If for any reason the issuer does not deliver such Notes, the underwriter will notify you, and neither the issuer nor any underwriter will have any obligation to you to deliver all or any portion of the Notes which you have committed to purchase, and none of the issuer nor any underwriter will be liable for any costs or damages whatsoever arising from or related to such non-delivery.

(vi) It is understood that the Underwriters will not enter into a Contract of Sale with any investor until the Approved Offering Materials have been conveyed to the investor with respect to the Notes that are the subject of such Contract of Sale.

(vii) Each Underwriter may prepare and provide to prospective investors Free Writing Prospectuses, subject to the following conditions to be satisfied by such Underwriter:

A. Unless preceded or accompanied by a prospectus satisfying the requirements of Section 10(a) of the Securities Act, such Underwriter shall not convey or deliver any Written Communication to any person in connection with the initial offering of the Notes, unless such Written Communication (i) is made in reliance on Rule 134 under the Securities Act, (ii) constitutes a prospectus satisfying the requirements of Rule 430B under the Securities Act or (iii) constitutes a Free Writing Prospectus consisting solely of (x) information of a type included within the definition of ABS Informational and Computational Materials, (y) Permitted Additional Materials or (z) information accurately extracted from the Preliminary Prospectus Supplement or any Issuer Free Writing Prospectus and included in any Underwriter Prepared Issuer FWP or any Underwriter Free Writing Prospectus.

B. Such Underwriter shall comply with all applicable laws and regulations in connection with the use of Free Writing Prospectuses, including but not limited to Rules 164 and 433 of the Securities Act Regulations and all SEC guidance relating to Free Writing Prospectuses, including but not limited to SEC Release No. 33-8591.

C. It is understood and agreed that all information provided by the Underwriters to or through Bloomberg or Intex or similar entities for use by prospective investors, or imbedded in any CDI file provided to

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prospective investors, or in any e-mail or other electronic message provided to prospective investors, to the extent constituting a Free Writing Prospectus, shall be deemed for purposes of this Agreement to be an Underwriter Free Writing Prospectus and shall not be subject to the required consent of the Trust Manager set forth in the third sentence in Section 5(a)(vii)(E). In connection therewith, each Underwriter agrees that it shall not provide any information constituting Issuer Information through the foregoing media unless (i) such information or substantially similar information is contained either in an Issuer Free Writing Prospectus or in an Underwriter Prepared Issuer FWP in compliance with Section 5(a)(vii)(B) or (E) to the extent such information consists of the terms of the Notes, the final version of the terms of the Notes or substantially similar information is contained either in an Issuer Free Writing Prospectus or in an Underwriter Prepared Issuer FWP in compliance with Section 5(a)(vii)(E).

D. All Free Writing Prospectuses provided to prospective investors, whether or not filed with the SEC, shall bear a legend including the following statement (or a substantially similar statement approved by the Trust Manager):

“THE DEPOSITOR HAS FILED A REGISTRATION STATEMENT (INCLUDING A PROSPECTUS) WITH THE SECURITIES AND EXCHANGE COMMISSION (THE SEC) FOR THE OFFERING TO WHICH THIS COMMUNICATION RELATES. BEFORE YOU INVEST, YOU SHOULD READ THE PROSPECTUS IN THAT REGISTRATION STATEMENT AND OTHER DOCUMENTS THE DEPOSITOR HAS FILED WITH THE SEC FOR MORE COMPLETE INFORMATION ABOUT THE DEPOSITOR AND THE OFFERING. YOU MAY GET THESE DOCUMENTS AT NO CHARGE BY VISITING EDGAR ON THE SEC WEB SITE AT WWW.SEC.GOV. ALTERNATIVELY, THE DEPOSITOR, ANY UNDERWRITER OR ANY DEALER PARTICIPATING IN THE OFFERING WILL ARRANGE TO SEND YOU THE PROSPECTUS AT NO CHARGE IF YOU REQUEST IT BY CALLING TOLL-FREE 1–8[XX–XXX–XXXX] OR VIA EMAIL AT                      .”

Upon reasonable notice and in consultation with the Underwriters, the Trust Manager shall have the right to require additional specific legends or notations to appear on any Free Writing Prospectus, the

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right to require changes regarding the use of terminology and the right to determine the types of information appearing therein. Notwithstanding the foregoing, this subsection will be satisfied if all Free Writing Prospectuses bear a legend in a form previously approved in writing by the Trust Manager;

E. The Underwriters shall deliver to the Trust Manager and its counsel (in such format as reasonably required by the Trust Manager), prior to the proposed date of first use thereof, (unless such timing requirement is waived by the Trust Manager), any Underwriter Prepared Issuer FWP (as defined above). To facilitate filing to the extent required by Section 5(a)(vii)(G) or Section 5(a)(i), as applicable, all Underwriter Derived Information shall be set forth in a document separate from any Underwriter Prepared Issuer FWP including Issuer Information. Consent to use of any Underwriter Prepared Issuer FWP must be given by the Trust Manager in written or electronic format before the Underwriter provides the Underwriter Prepared Issuer FWP to investors pursuant to the terms of this Agreement. Notwithstanding the foregoing, the Underwriters shall not be required to deliver or obtain consent to use an Underwriter Prepared Issuer FWP to the extent that it does not contain substantive changes from or additions to any Underwriter Prepared Issuer FWP previously approved by the Trust Manager. In the event that an Underwriter uses any Underwriter Prepared Issuer FWP without complying with the foregoing requirements, that Underwriter Prepared Issuer FWP shall be deemed to be an Underwriter Free Writing Prospectus for purposes of Sections 7(a) and 7(c);

F. The Underwriters shall provide the Trust Manager and the Issuer Trustee with a letter from PricewaterhouseCoopers LLP, certified public accountants, prior to the Closing Date, satisfactory in form and substance to the Westpac Parties and their counsel and the Underwriters, to the effect that such accountants have performed certain specified procedures, all of which have been agreed to by the Trust Manager and the Underwriter, as a result of which they determined that certain information of an accounting, financial or statistical nature that is included in any Underwriter Prepared Issuer FWP, other than any Pool Information therein and any information accurately extracted from the Preliminary Prospectus Supplement or any Issuer Free Writin