Arthur Balfour is a daunting prospect for the biographer because of his openly expressed doubts about the whole genre. As he once confided to a friend, he could tolerate criticism and was vain enough to enjoy a little praise from time to time, but he had ‘moments of uneasiness’ when he was ‘explained’. As an emotionally reticent man, the whole idea of being put on show was mildly distasteful. But it was an inevitable fate for someone who was in public life for over half a century, and, in R J Q Adams, Balfour has found as solicitous and understanding an apologist as he could have wished for.

Balfour was one of the last men to come from a world in which politics was an inheritance. Capable or incompetent, stupid or wise, someone with Wellington as a godfather and Lord Salisbury as an uncle was bound to have options in public life. The phrase ‘Bob’s your Uncle’ was