How did the Norwich Union, a life and general insurance company, come to see itself as a ‘local developer with people always at the centre of our planning’? This article explores how a small number of insurance companies, capitalising on their long history of property investment, used their investment funds, or ‘life funds’, to transform the built environment of UK in the twentieth century. In the postwar period life funds were contracted by local governments to finance, plan and develop solutions to urban issues that paralleled those targeted by post‐war welfare reforms. This involved companies in developing expertise, working practices, instruments and collaborative arrangements that are not adequately represented as financial investment. Ventures into development on this scale had also to be ventures in futures planning, calculated bets on how people would – and how they should – live, work and spend. These are enterprises that I characterise as ‘experimental practices of financial sociology’ as a provocation that acknowledges first, that non‐sociologists sometimes devise huge sociological experiments and second, that the separation of economics from sociology, and of finance from society, is a disciplinary move that is far less strictly enacted outside the academy.