What is Britain’s biggest physical export? Given that the UK has some of Europe’s most advanced car factories, you might have assumed the answer was motor vehicles. Or perhaps pharmaceuticals, or engines, or crude oil from the North Sea?

No. In July, the latest month for which we have the figures, Britain’s biggest physical export was gold.

That might, on the face of it, seem a little odd. Britain has no substantial gold mines. It has barely any refineries, save for those which melt down scrap metal or mint souvenir coins. The vast majority of the world’s gold is, of course, dug out of the ground elsewhere: in South Africa, the US and Canada. So why, when we look at the world’s biggest gold exporters,