But the world has moved on since the 1930s when Keynes evolved his most important theories. His own defiant dictum, that he changed his mind when the facts changed, has been on the lips of current policy-makers. There never was a timeless “Keynes” whose every utterance had prophetic force. There was instead a historical Keynes who came up with lots of bright ideas as he confronted different problems.

This is why Keynes supported the New Deal measures of Franklin D. Roosevelt in the depression-stricken US of the 1930s. The openness to experiment that Roosevelt displayed under pressure of events was something that appealed to the similar can-do temperament of the British economist, whose name was then applied in a manner that can best be termed inventive.

True, the New Deal meant public works programmes that Keynes had long advocated in response to the slump in Britain. It was common sense to put idle resources to work. Savings otherwise not invested and workers otherwise left unemployed, could create valuable public assets if government took the initiative.