This thesis is an ethnographic study of UK environmental social movement mobilisations of the 1990s, detailing the movement's characteristics such as its structure as a fluid series of biodegradable networks. The thesis evidences what action was taken during this period, using primarily qualitative methodologies: semi-structured interviews and Participant Observation (PO). Evidence showing how mobilisation occurred, how activist networks are 'born' and sustained, is given, examining issues such as the diffusion of repertoires over time, and the importance of social networks. The "why" of mobilisation was documented, detailing activists' rationales for action given in interviews and a variety of other media such as email groups and in PO settings. The thesis approached the data from a 'grounded theory' perspective, meaning that appropriate theoretical directions developed during the research process. There were however initial aims: to investigate whether the EDA movement had a 'collective identity' (Melucci 1996), and hypotheses: that activists had complex rationales for taking action, and that there was a symbiosis between the taking of action, the development of movement praxis and collective identity, and the process of further mobilisation. These aims and hypotheses were realised by the research work. Despite many complexities outlined in the research, generally the EDA movement has a collective identity. This is based on a shared commitment to direct action, grassroots democracy, and a radical discourse, which challenges the codes and perceived abuses of power inherent in the dominant paradigm. Social justice, human rights, and environmental sustainability are equally important to EDA activists and seen as interrelated. Through charting the process of action in the 1990's, the thesis locates the 'anti globalisation' mobilisations at the turn of the millennium as evidence of EDA movement capacity building over a decade. The thesis aims to have contributed to Social Movement theory through this ethnographic approach.