Boris needs a minister for banana skins

Every prime minister needs a Willie, said Margaret Thatcher to a soundtrack of great national tittering.

She was of course referring to William Whitelaw, her massively experienced deputy upon whose advice she relied to moderate her zanier impulses and views.

Whitelaw fitted the bill as a non-ideological Conservative who had pledged his loyalty to her and genuinely had no further hankering for the top job himself, having been roundly defeated by Thatcher in the Tory leadership contest of 1975.