IF there is one law that politicians all over the world would like to see repealed, it is the Law of Unintended Consequences. Just look at what it has done to our efforts to tackle global warming. In the rush to produce biofuels, we have accidentally raised food prices. So we might just save the planet, but a celebration dinner will be out of the question.

History is littered with unintended consequences. The treaty of Versailles, designed to end one war, inadvertently created the conditions for another. When Henry VIII filed for divorce, he inadvertently created the Church of England, the organ fund appeal and the Vicar of Dibley. Gordon Brown cut the 10p tax rate to set a political trap for the Tories, but managed to plunge headlong into it himself.

It is a law that seems to apply uniquely to politics. Consequences unforeseen by political leaders seem obvious to everybody else. Especially afterwards. But it’s a law that we are obviously stuck with. After all, if we found a way round it, something unforeseen would only go wrong. That’s the law.