This chapter examines the historical development of the European Union (EU) and the roles played by its major institutions. It also explains the policies pursued by successive British governments towards the EU. Within the EU, the UK has often been considered an awkward partner, wary of deeper political and economic integration. Domestically, the UKs relationship with the EU remains a major issue that has caused divisions between and within the main political parties. EU institutions and policies would have to be reformed if a wider Union was to function effectively. The European Communities Act 1972 gave future EU law legal force in the UK and denied effectiveness to national legislation which conflicts with it. David Cameron's commitment to renegotiation and a referendum was, in large part, a response to the challenges of party management and party competition, but it has potentially momentous consequences for the UK, the EU and the Conservatives.