Back in the 1980s, Tony Blair, a junior Shadow minister, was sitting quietly with his constituency agent, John Burton, when he suddenly exclaimed: “You know, John, I understand it all. Finally, I've got it.” When Burton asked him what he was talking about, Blair triumphantly replied: “Microeconomics!”

I wonder whether in a couple of decades' time, our own fumbling first acquaintance with new thinking will appear similarly amusing. For an intellectual revolution is under way that will change the way we think about public policy just as the free market economists did in the 1980s. I wonder whether one day soon a future party leader will turn round to his agent and say: “Finally, I've got it! Human behaviour.”