This article examines the careers of a number of left thinkers who broke with the Communist Party of Great Britain in the late 1930s, committing themselves instead to a ‘politics of everyday life’ based on social investigation. Central to this moment was the social research organisation Mass-Observation, the sociologists of which argued that democracy should be built around the vibrancy and irreverence they identified in ordinary culture. This ambition gained its fullest application during the 1940s, as a number of former M-O researchers became influential in the social reconstruction effort, in Labour Party policy circles and, later, in post-war academic sociology. By tracing the sociological arguments of unaligned left intellectuals from the 1930s to the 1950s, this article emphasises the rich plurality of influences at play within British progressive thought in the mid-twentieth century—influences which spanned the worlds of far-left activism, literature, art, the social sciences, town planning and parliamentary politics. It also helps us to reassess the genesis of the first ‘New Left’ in 1956. This is often hailed as the moment when British socialists first started to appreciate ordinary culture, freed from political dogmatism. In fact, left intellectuals had been engaging with the politics of everyday life for at least two decades previously. Indeed, the nostalgic accent which some New Left writers placed on the traditional working-class group was but one facet of a more heterogeneous political tradition—one concerned to think beyond ‘class’ altogether, and to examine how culture operated at the level of the individual.