Referendums in the UK are extremely rare due to the principles of parliamentary sovereignty. To date, there have only been two – the first on membership of the EEC in 1975 and the second on adopting the Alternative vote system in 2011. The fact that there’s been two referendums in 5 years shows there may be changing attitudes in the UK as both were results of appeasing the post-General Election pressure from non-elected parties with increasing support – in these cases, the Liberal Democrats in 2010 and UKIP in 2015.