“Export or die!” exhorted the posters tacked on to the walls of British factories in the years after the second world war. Back then, there was an immediate imperative to shovel goods abroad. Britain, heavily indebted by the war, needed to earn foreign currency to back sterling in the newly created Bretton Woods exchange rate system.

These days, there should be a far less pressing need for the export powerhouses – Germany, China, Japan – to be quite so seized by the grip of mercantilism. Yet while global international commerce is imploding, there are worryingly few signs that trade is being rebalanced rather than simply shrunk in its current ­pattern.