This chapter demonstrates how the theory of micro-mobilisation applies to and explains the emergence of punk in London during 1976. The theory of micro-mobilisation begins with the claim that the collective action generative of a music world requires a critical mass of suitably motivated and resourced potential participants. The chapter offers a preliminary analysis of the social network which underpinned the London punk world. It argues that punk took shape in London appears to have had their own critical mass of proto-punks, because the critical mass of proto-punks in the capital formed a network. A network is a crucial prerequisite of any form of collective action. Manchester had a critical mass of proto-punks in the mid 1970s, which assembled to generate a punk world within months of first making contact with the London punks.