When I was about 15, alone in the flat one afternoon, I sneaked into my mother’s writing desk and found a small pocket calendar from 1946 pushed to the back of a drawer. I had grown up with my mother and her parents, not knowing who my biological father was, or how I had come about; the question was simply never asked. I turned, with a kind of dread, to the entries from nine months before I was born. In mid-March there was an ordinary note – ‘Party at the Academic Association’; she was training as a laboratory technician in Lund and liked the students’ company – and on the following day, in her hand, five words: ‘God, what have I done!’ I still remember the shock of standing there with the diary, half-guilty for trespassing on her private papers, and saying aloud, over and over: ‘That’s me – that’s me. What have you done? I’m a mistake.’

For half a century, the scene stayed as it was: fixed, private, finished.…