In old-fashioned crime novels, the residents of a sleepy English village are occasionally scandalised by a spate of anonymous letters. It’s usually small stuff, about supposed affairs or minor financial transgressions, but the effect is devastating. In the modern world, it’s all much easier: no need to go to the bother of disguising handwriting or cutting letters out of newspapers. There’s something about the Internet that seems to give people permission to send malicious emails or post poisonous words online. They adopt self-aggrandising pseudonyms or don’t even bother to hide their identities; the chances of being punished are not that high, and the impact – to a deranged mind at least – is intensely satisfying.