The European Union (EU) consists of the largest group of advanced industrial economies in the world. Its origins can be traced to plans that were set down in the interwar period of the 1920s to overcome tension between European countries. The main impetus to European integration was the legacy of the Second World War and the desire to rebuild European countries through a process of external support that would avoid future conflict. Over subsequent decades the process of European integration accelerated through a widening of membership and deepening of policies. This movement to what European treaties have referred to as “ever closer union” has, nevertheless, created tension between member states and also between the institutions that govern the EU and its member states. It is a state of affairs that has resulted in an increase in support for political parties that challenge further European integration and who seek to return more powers to member states by reclaiming national sovereignty. The most significant development of this was the decision taken by the United Kingdom (UK) electorate to leave the EU in a referendum vote that took place on 23 June 2016. This development has led to significant turbulence within the EU and raised questions over the future direction of European integration.