I am running a four-day memoir-writing retreat in southern Spain, and using it as an opportunity to test out my theories. Of the ten participants, nine want to write a book and one is here by accident because she misread the small print. Having thought she would be able to snooze her way through the day and sample the local tapas in the evening, she’s wandered into something resembling an Agatha Christie novel, where a group of strangers, thrown together in an isolated house, are all harbouring murderous thoughts.

Which brings me straight to my first theory: most memoirs, if not loaded guns, are written for the purpose of retribution and revenge. This is by no means a criticism: retribution and revenge are strong reasons for writing a book. You want to put the record straight, to tell your side of things, to correct a wrong. Even the mildest-mannered memoirs have reprisal at their hearts. A memoir of midlife marrow growing may well be a missile directed towards a particular person, such as the teacher who gave you bad marks in English. On the other hand, the memoirist might, like Princess Diana in Her True Story, the autobiography