‘I merely attend to the progress of my Life of Johnson’, wrote James Boswell in his journal on the eve of his fiftieth birthday in 1790. Every biographer knows that feeling: when you are in the middle of your work, perhaps at that crucial stage when you lie awake at night, wrestling with a mass of disparate detail, and finally begin to feel that a convincing picture of your biographical quarry is emerging. Then everything else goes out of the window.

Adam Sisman has written a magnificent study of that obsession– the story of how Boswell, the priapic, insecure son of the Scottish judge Lord Auchinleck, struggled to collate the life of his very different friend, the solid, irascible, Englishman of letters, Dr Samuel Johnson. As Sisman describes , Boswell had