This thesis examines in detail the operation of a planning gain policy in the London Borough of Tower Hamlets between 1971 and 1983, using data obtained from records held at the Borough and observations of the practice. The practice of planning gain is set into the broader context of planning and the still broader social and political context. The existing literature and definitions of planning gain are critically examined in the light of a theoretical framework which concerns itself with the identification of power and politics within the planning process. The responses made to the practice of planning gain by the Department of the Environment, planning inspectors and the courts are explained and critically analysed to indicate the lack of articulated opposition. The use of planning agreements as a mechanism for the enforcement of planning gain is also examined. Section 52 of the Town and Country Planning Act is analysed, together with the available case law. The use of these agreements in Tower Hamlets is discussed in detail. The schemes examined at Tower Hamlets are presented in full to provide an overall view of the operation of a planning gain policy. Details include the effect of negotiation on the content of schemes and problems of implementation. Comparative material is provided covering the operation of a planning gain system which has legislative recognition in Sydney, Australia. This part of the thesis is used to illustrate the continued existence of negotiation for planning gain and of the restrictive responses to the autonomy of local government.