There’s nothing so ex as an ex-Prime Minister. But while the likes of Boris Johnson, Liz Truss and David Cameron are busy off respectively writing columns, making speeches and, er, running the Foreign Office, Theresa May has been content to quietly reside on the backbenches. As MP for Maidenhead, she has spent much of the past year promoting her new book – Abuse of Power – which proved to be the best-seller at October’s party conference.