The human tendency towards loss aversion is mostly studied by economists and psychologists, but it’s politicians who should pay it most attention. Loss aversion is the basis of an iron rule of modern politics: once you give people something, it’s fearsomely difficult to take it back.

The BBC has been proving the point recently, as small crowds of angry pensioners gather outside its offices to protest at the end of free TV licences for the over-75s. Most politicians have tried to keep out of the row, letting the corporation take the heat for a decision many quietly regard as prudent and maybe even fair. Not everyone over the age of 75 needs a free licence, while quite a few under that age are more in