I joined what looked like a short queue at Tesco. There was one person having her goods scanned and one other set of items on the belt.

Then, in swooped a man with a basket to join a sleeper agent in the line in front of me. I had thought that she was with the person in front, but no: she was just there to keep the place while her partner did the shopping.

What nerve! What an inexcusable breach of etiquette! They weren’t from round here, though that’s no defence. I did the only British thing. I tacitly accepted the situation, queued patiently and moaned about it later.