In England, for over three decades planning obligations have been the main mechanism by which non-market housing has been delivered. Since around 2005, at the local planning authority level, tests of the financial viability of development projects have become a central consideration in planning policy making and development management concerning the provision of non-market housing. In essence, ostensibly to ensure that development is deliverable, a financial viability test involves a quantitative calculation of whether policies regarding requirements for non-market housing compromise a "competitive" financial return to the land owner and the developer. In a period of high levels of innovation and/or volatility in the English planning and housing policy regimes, this has been a fundamental change in the planning system. The research investigates changes in the supply of non-market housing in London in terms of its level and composition. Drawing upon data obtained from the Greater London Authority’s Development Database, the research investigates the relationship between national policy adjustments relating to housing and planning obligations, the supply of affordable housing, and land value capture in London and how this has evolved in the last decade.