Theresa May is but the latest victim of Britain’s ill-fated engagement with the Continent. Europe has proved toxic for the Conservatives, ruining six of their last seven Prime Ministers.

Harold Macmillan was the first, when, in 1963, President de Gaulle vetoed his application to join the European Community, as the EU then was. “All our policies at home and abroad are in ruins,” Macmillan wailed. De Gaulle correctly predicted that Labour would win the next election. His information minister, Alain Peyrefitte, records him as slicing the air with the back of his hand, “as pitiless as a Roman emperor turning down his thumb as though denying a reprieve to a defeated gladiator”, and saying “That Macmillan vanishes!”.

It was Edward Heath who took us into Europe in 1973. But, in the February 1974 election, he was narrowly defeated. A host of factors could have been responsible – but Enoch Powell, who broke with his party and urged voters to support Labour to secure a referendum – plus ça change – was undoubtedly crucial in Heath’s defeat.