I heard of Isaiah Berlin more than twenty years before I met him. When I went up to Oxford at the age of nineteen, in 1949, there was a handful of luminaries in the humanities who were known to us all and thought to be stars. In history, vying with one another, were A. J. P. Taylor, A. L. Rowse and Hugh Trevor-Roper. Taylor, the outstanding lecturer of the three, and perhaps the best in the university, used to perform in the largest hall at the most unpopular hour and day (nine o’clock on a Saturday morning) to demonstrate that he could fill it when no one else could. In the English faculty the comparable figures were Lord David Cecil, C. S. Lewis, and, just beginning to come into his inheritance, J. R. R. Tolkien. But in philosophy there was only Isaiah Berlin. In our little world these were glamorous figures, public intellectuals whose reputations had spread beyond their subjects. They were known not only outside Oxford but outside the academic world altogether, and this gave them a special prestige in our eyes. Unlike nearly everyone else in the University, these were people whom other people had heard of. It was as one of the stars in this firmament that I first became aware of Isaiah.

The difference between him and the others was that they had all published what were considered to be distinguished books, and their striking personalities came on top of that. Berlin had indeed published what was to be his one and only full-length book, but it was a lightweight affair that did not pretend to be anything else, a popular biography of Karl Marx in a non-academic series. This meant that his reputation rested on nothing but his personality. He was perceived as hyper-bright – brighter, perhaps, than the others – and the most brilliant of conversationalists. It was this, we supposed, that had gained him his reputation in the outside world. However, his talk was said to be not so much entertaining as formidable, even daunting.

As a student I did not lead a primarily academic life, and did not move personally in those circles. But I saw these rare individuals around the place, and heard anecdotes about them, and read some of their books, including Berlin's biography of Marx. I found it, as people said, lightweight.