Come and see the toad,’ said seven-year-old Charlie. I humoured him by walking down the steps into our Pimlico road. There, sure enough, was a large toad. A real one. (It’s a sad reflection on the times that our eldest son, William, thought it was a toad-shaped security device installed by the tenant in our basement flat.) How on earth did it get there? The nearest toad-supporting habitat is St George’s Square but only a very lucky toad could have hopped across two London roads without being flattened.

William’s unfortunate penchant for dropping defunct computers from our balcony to see what will happen has broken the cover to the rainwater drain; but a toad could hardly have made the foot-high vertical leap from the water surface. Besides, do toads live in sewers? Surely not.

‘A bird must have dropped it,’ proposes one friend. ‘Or perhaps it was discarded by a child, who got tired of it,’ suggests another. Next day, the toad had gone, as mysteriously as it appeared. Toads are meant to be witches’ familiars. I think Prof McGonagall has been having fun with me.