By the criteria of the day before yesterday, the late William Whitelaw, a much loved Tory politician who served as Mrs Thatcher's deputy leader, must have seemed a good circulation bet for a successful biography. Most people, after all, would have heard of him, if only because of Mrs Thatcher's memorable remark that 'every prime minister needs a Willie'. In addition, however, to acting his most valuable role as a restraining influence on Prime Minister Thatcher, he was also a controversial Secretary of State for Northern Ireland, a well-thought-of Home Secretary, Chief Whip and leader of the House of Lords, not to mention a second world war hero and a very perfect model of a public-spirited, land-owning Tory grandee of the calibre and character which used to provide the old ruling class with its ballast and 'bottom'.