It is said of Harold Wilson that he epitomised the quip: “If you can’t ride two horses at the same time, you shouldn’t be in the circus.” He was often criticised for putting pragmatism before principle in his 13 years as Labour leader, but it was an attribute that served him well in preventing the party from tearing itself apart on Europe in the 1970s.

When Wilson won a fourth general election on 10 October 1974, he faced the challenge of navigating Labour’s deep divisions on whether or not to reverse the 1972 decision to join the common market. The party’s election manifesto had promised the British people a “final say” on Britain’s membership without committing itself one way or another to a recommendation. “It is as yet too early to judge the likely results of the tough negotiations which are taking place,” it said.