My elderly mother has come to live in a little row of terraced houses three minutes from where I live, so that I can keep an eye on her. This is a polite fiction, sustained by both of us to keep up appearances; in reality, aged 87 and with short-term memory loss, she needs care. Hey presto! Daughter appears on stage.

This blog is not actually about my mother. I mention her because in the course of tripping back and forth a few times a day on filial duties I have to pass one of the other terrace houses two doors from where she lives. On Boxing Day, on one of my expeditions, I happened to bump into its occupant: a lady of indeterminate age and indeterminate dress, the sort of person you might sit next to on a bus and not recall anything about them.