A major environmental campaign currently in progress in Northern Ireland opposes a £40 million road development scheme, which foresees the upgrading of the ‘M1/Westlink corridor’ by building flyovers and extra lanes. This profile tackles the complex task of mapping and analysing both the significant links amongst the actors which have mobilised, and their systems of alliance. The main focus of my argument, therefore, is on the pattern of social relations that have been developing through overlapping memberships and alliances amongst groups participating in the Westlink campaign. Indeed, some political scientists consider the analysis of development and consolidation of social networks (upon which a movement is based) as an alternative and more significant instrument for assessing the novelty (and the real strength) of social movements’ challenges to dominant actors in contemporary societies. Under this perspective, social movements are networks linking a multiplicity of actors (individuals, groups and formal organisations) [Diani, 1992], which are to be evaluated through a detailed appraisal of the broader social context within which they develop [Diani, 2001] (...).