This article explores the historically specific use of cosmetic commodities as evidence in prosecutions for importuning in interwar London. Taking as its point of departure the story of ‘the man with the powder puff’ told in the journal John Bull in 1925, it moves to consider the discrete but intersecting histories within which cosmetics came to function as a material sign of deviant masculinity, illicit sexuality, and de facto criminality. The process through which a powder puff could be deployed as evidence in court depended upon a particular understanding of sexual difference. It was embedded in the emergence of a vibrant consumer beauty culture in the 1920s. It took shape within the operational practices of the Metropolitan Police, particularly the explosive politics of law enforcement after the First World War. It emerged, finally, in response to profound anxieties about the war's disruptive impact on British culture. In understanding the story of ‘the man with the powder puff’, I argue, we might more fully understand the cultural landscape of post-First World War Britain.