Forgive me for starting with a quote. It’s from the late John Biffen, an important if ambiguous figure through the Thatcher years. Biffen is recalling his ringside seat on the night when the Commons debated the government’s handling of the Profumo affair; the night a speech by Nigel Birch MP blew the starting whistle on his prime minister’s demise. Mr Birch was an independent-minded Tory of some standing. At 6.17 on June 17, 1963, Birch rose to speak.

“His real target,” wrote Biffen, “he kept for the closing passage of his speech. He absolved Macmillan from such harsh charges as dishonour but suggested his leadership faculties had aged beyond recall. ‘I myself feel that the time will come very soon when the prime minister ought