David Cameron — former prime minister, ex-leader of the Conservative party, brown hair, about 6ft tall, perhaps you remember him — was apparently of the view pre-referendum that among his cabinet colleagues there were only two figures with the temperament and skills required to succeed him in office. The first was his friend and partner in the Tory modernisation project, George Osborne, then the chancellor. The second was Theresa May, the no-nonsense home secretary who in Mr Cameron’s view supposedly got things done and was a poker-faced nightmare to negotiate with. What Mrs May ever got done, exactly, as home secretary remains one of the enduring mysteries of the Cameron government, which is of a piece with her reputation as an unknowable conundrum and all-round