Margaret Thatcher was said to have once remarked that every prime minister needed a Willie. Given that humour was not her natural domain, perhaps she didn’t even intend it as a pun. The Willie she was referring to was, of course, the vastly experienced William Whitelaw who served as her effective deputy – and most famously as ‘minister for banana skins’ – for almost a decade despite being from the patrician and ‘wet’ side of the Tory party.