ROY PORTER WAS a friend of mine. We studied at the same Cambridge college, specialised in the same period (the eighteenth century) and, when it came time to leave Cambridge, each found a home in London, he at University College, I at King's. But there the similarities end; for, although I have spent the past thirty years producing a modest total of books, films and papers, Roy was tirelessly productive. The endpapers of this book, reprinting sections of obituaries, speak of him as 'inexhaustible' (Guardian) , 'indefatigable' (Sunday Times) and 'superhuman' (London Review of Books). The text of the book was completed just a week before he died and represents his final statement on medical history - the subject that he had made his own.

The sense of an inuninent end seems to have been with him as he was writing this. How else can one read his chapter on Dr Johnson, who also wrote ceaselessly, being our first parliamentary reporter (thinly disguising his subject by calling the Houses of Parliament, quite appositely, the Senate