Some say that the first hints that Bill Bryson was not of Planet Earth came from his discovery, at the age of six, of a woollen jersey of rare fineness. Across the moth-holed chest was a golden thunderbolt. It may have looked like an old college football sweater, but young Bryson knew better. It was obviously the Sacred Jersey of Zap, and proved that he had been placed with this innocuous family in the middle of America to fly, become invisible, shoot guns out of people’s hands from a distance, and wear his underpants over his jeans in the manner of Superman.