There was a time when boys had hobbies. They collected stamps, pinned dead butterflies to strips of balsa wood, stole eggs from birds’ nests, painted model aircraft and toy soldiers, and spotted trains. The point about hobbies – whether indoor or outdoor – was that they had to be slightly obsessive. To have a hobby was to belong to a club of other obsessives, with rules and rituals and due process.

For me, it was fishing; for Richard Kerridge, it was amphibians and reptiles. He writes beautifully about how the germ of his obsession took hold as a boy in an outwardly normal family in an ordinary London suburb. There were no interesting birds of prey or large mammals around. But