We visited friends in Wiltshire over this most recent weekend. Over a game of mah jongg the subject of imagination came up. “Well, of course,” said Belinda, “I don’t have an imagination – never had.” I tucked the remark away for later dissection. This week on the water I think what Belinda was saying is that she has never dreamt up stories about people and events that don’t exist in the real world. But I suspect that imagination is much larger than that. Let’s start at the beginning with a...