Confessions of a teenage existentialist: back in the early 1970s, when my mates and I were all revving up for A-levels, Jean-Paul Sartre was, simply, the most famous of all living philosophers, and just about the most famous of all proper, serious writers. He was inevitable, compulsory, ubiquitous. You didn’t even have to be a swot to have a fairly good idea of who he was, since BBC2 had just devoted 13 solid hours of prime-time viewing to its dramatisation of the Roads to Freedom trilogy. (Thinkable nowadays?) The Monty Python gang performed a Sartre sketch and for weeks afterwards, schoolyards echoed to imitations of Mrs Premise’s high-pitched telephone query to Sartre’s (fictitious) wife: “Quand sera-t’il libre?” Pay-off: “She says he’s spent the last 60 years trying to work that one out!” Oh, we did laugh.

If you did happen to be a swot and/or would-be intellectual, Sartre was even