There is a phrase that has been fashionable for years in wonkland — places like the upper echelons of the civil service and high-end think tanks. The phrase is ‘evidence-based policy-making’. There, I bet that’s got you going.

When I was a citizen of wonkland and heard those words from the Sir Humphreys and Lady Susans I would typically roll my eyes or head for the door, because you can generally gather whatever evidence you want to justify whatever policy you want.