The build-up to BrexitThe UK first joined the European Economic Community (the forerunner organization to the EU) in 1973, after spending years on the sidelines of European integration. Due to political divisions about membership however, a referendum was held two years later in 1975, which was ultimately won by those campaigning to stay in the European community. Opposition to membership continued nonetheless, and expressed itself most obviously in the creation of the United Kingdom Independence Party (UKIP). In the 2014 European Elections, UKIP won the highest share of the vote, and probably forced the hand of the Conservative Prime Minister, David Cameron, to promise a referendum on Britain's EU membership should he win re-election in 2015. After winning a decisive majority in the 2015 General Election Cameron set out to renegotiate more favorable terms of with the EU, and then to hold a referendum on membership in 2016.
After securing what he believed to be significant concessions from the EU, Cameron campaigned to remain in the organization, although the issue split his government down the middle, and key allies such as Boris Johnson notably joined the leave side. In the weeks leading up to the referendum, opinion polls indicated that the vote would be close, whoever should emerge victorious. While the remain camp focused on the economic impact of Brexit, leave campaigners highlighted the cost of EU membership, claiming that 350 million pounds a week in recuperated costs could be spent on the NHS, with this claim famously written on the side of giant red bus. One week before the vote, UKIP-leader Nigel Farage faced widespread criticism when he unveiled an anti-immigration poster which featured a picture of refugees and the words ‘breaking point’ on it. On the same day, the Labour MP Jo Cox was assassinated on the streets of her constituency by a far-right extremist, putting a temporary halt to the campaigning just one week before the referendum.