Trolls, as any three-year-old can tell you, lurk underneath structures they didn’t build and pop up at unexpected moments to get in the way and make unreasonable demands. And “patent trolls”? They do much the same thing, nosing around patent systems and buying up intellectual property, often of questionable quality, and using it to extort money from genuinely innovative companies by threatening protracted and expensive legal action.

I am sympathetic to the general point that many patents, and their potential for abuse, actively discourage innovation. But if we’re to solve the problem, it’s worth pinpointing where it lies – and the rise of the trolls is a symptom, not the cause.

The three pillars that enable patent trolling are: the existence of