This chapter assesses British party policy (as expressed in general and European election manifestos) and public opinion (using Eurobarometer data) towards the enlargement of the EC/EU. The chapter first analyses party and public support for enlargement, including the various enlargement rounds in the 1980s, 1990s and 2000s. It then investigates attitudes towards the conditions that prospective member states were required to fulfil and the perceived consequences of EU enlargement to central and eastern Europe. The chapter shows that Britain’s governments and its main parties were consistent, steadfast proponents of EC/EU enlargement. Further, the three main parties principally saw enlargement as a means to embed democracy and respect for human rights, and to strengthen security within Europe. This political support for enlargement came at a domestic cost though. Having previously been less enthusiastic than the political establishment, from 2006 the British public came to oppose the idea of further EU enlargement. Signs of enlargement’s potential to be a controversial issue among public opinion existed ahead of the EU’s 2004 expansion too. This is evidenced by the public favouring prospective member states fulfilling strict criteria prior to joining, and public concerns about economic costs and migratory pressures—matters that received less political attention.