Although Brexit had its short-term roots in economic and constitutional legitimation issues, it cannot be explained without considering the European geopolitical space, the EU’s contrasting political formations in the security and economic spheres, and the fault lines these produce. Seen from a long-term geopolitical perspective, there have been recurrent problems in Britain’s efforts to deal with the EU and its predecessors, and persistent patterns of crisis. The geopolitical environment, especially around NATO and energy security in the Middle East, first rendered non-membership of the EEC a problem, then made entry impossible for a decade, helped make EU membership politically very difficult for British governments to sustain, and the constrained the May governments’ Article 50 negotiations. These problems have a singularly British shape, but they cannot be separated from more general fault lines in the European geopolitical space.