Recent developments in British politics have once again brought to the fore the UK’s troubled relationship with, and within, the European Union. We have seen the extensive mobilization of Eurosceptic forces including rebellions in the Conservative Party and the rise of the UK Independence Party (UKIP) to national prominence. In 2013, David Cameron responded to political pressure and committed a future Conservative government to holding a referendum on British membership. The Party’s election victory in May 2015 confirmed that this would take place before the end of 2017 following a renegotiation of the terms of British membership. With the prospect of a referendum, commentators began to seriously debate the possibilities of a British exit, and the UK’s options outside of the EU. Meanwhile, public opinion was more sensitized to British membership than it had been seen for some time as intra-EU immigration became politicized, when free movement was opened up to Bulgarians and Romanians. In sum, an extensive domestic Eurosceptic mobilization has had direct implications for European policy and the UK’s future as a European member-state.