This chapter explains how the powerful issue dimensions of the EU and immigration were combined in the 2004 decision for open immigration with EU accession countries. As immigration rose in the 2000s, the salience of immigration increased substantially. The 2004 immigration decision had two key consequences. Firstly, it greatly constrained the ability of UK governments to change the level of immigration in response to public opinion, and secondly, it closely linked the previously separate issues of immigration and Europe. The salience of immigration was related most strongly to media coverage of the issue, which in turn closely tracked the actual rates of immigration. UKIP capitalized on this combined EU/immigration dimension and substantial numbers of voters switched to UKIP from the major parties in 2015 on this basis. We show that without the high salience of immigration between 2010 and 2015, the defections to UKIP would have been relatively small.