The outcome of the Brexit referendum in June 2016 – a narrow majority for the United Kingdom (UK) to leave the European Union (EU) – came as a surprise to most commentators and participants. Eighteen months after the referendum, Brexit had already posed massive challenges to the UK State. This chapter discusses the UK's recent constitutional development and considers the role of EU law in UK constitutional change. It explains how patterns in public administration and political economy shape the prospects for the UK State as it negotiates its way through Brexit. Two longer-term aspects of the UK political sociology helped to shape the context of the Brexit referendum. The first concerns the treatment of the EU issue by Britain's two largest political parties. Second, these parties have found it difficult to address questions of national identity across the UK, particularly in England. For most of the twentieth century, political parties were central to the democratic operation of Western states.