This chapter explores the relationship between the UK and European integration in more detail. It begins with a short summary of the European Union (EU) — what it is, what it does, how it does this and what its strengths and weaknesses are. The chapter explores Britain's engagement with other forms of postwar cooperation in Europe and discusses the reasons for British reluctance to commit to the early phases of the integration process. The chapter looks at how the British—European relationship is unfolding after the referendum, with a particular focus on the impact on the European Union and on the likely shape of future EU—British relations. It examines the record of Britain after its accession, where it was often described in unflattering terms: as an 'awkward partner', as 'reluctant', as a 'stranger in Europe'. It was a European war that led to the foundation of what is now the European Union.