Every year in British politics seems to be more surprising than the last. Few predicted in 2015 that the Conservatives would win a general election outright for the first time in 20-odd years. Fewer still realised that Theresa May would become the most popular Prime Minister since records began. And almost no one foresaw how the tide would turn against her so dramatically that the Tories would lose their majority, or that Jeremy Corbyn’s Labour would make such significant gains.