Hang out with both trainspotters and opera buffs and you’ll soon notice that opera buffs are by far the more trainspotterish. It’s the pedantry, the one-upmanship (‘Really? You should have heard it with Goodall in 1976’). Above all, it’s the impulse to collect. You can’t actually buy little pocket books with lists of obscure operas to be underlined in biro once you’ve seen them (blue for a full staging, red for a concert performance) but there are certainly opera-goers who compile their own lists of personal stats – and they let you know it.