My mate Karl once told me he’d been looking after this five-year-old boy who – not knowing enough to have an ironic inflection to his words – said, ‘I want something.’ He didn’t know what it was. Not ‘I want sweets’, or ‘a can of Coke’, or ‘to watch the Tweenies’, or whatever it is they’re into now (I like Bagpuss), but ‘I want something.’ All of us, I think, have that feeling. And what heroin does when you first start taking it is tell you what that something is.