Can immigration impact electoral outcomes and specically, what impact did immigration have on the vote in favour of leaving the European Union (Brexit) in the UK? In particular, I focus on how the increase in Polish immigration, the major group of immigrants post 2004, affected votes in favour of leaving the EU. I find a percentage point increase in Polish immigration to the UK to have caused an increase in votes in favour of Brexit of about 2.72-3.12 percentage points, depending on the specification. To obtain exogenous variation in Polish immigration, I use a novel instrumental variables approach that relies on the fact that after WW2 Polish army ocers fighting in the Royal Air Force were quasi randomly allocated to War Resettlement Camps all across the UK. Discussing potential mechanisms, I examine public opinion data in the British Election Study 2015 and nd evidence of adversity towards immigration to be a root cause. Other considerations such as the National Health Service (NHS), incumbency and the general trust in politicians as well as the political institutions seem not to play a role.