Trade wars and geopolitical tensions have increased the appeal of the Swiss franc, the yen, and, to some extent, the dollar. But the real star is gold. After a nearly 15% price rise in less than three months, the yellow metal sells at around $1,500 per ounce - levels last seen in 2013. The gains are all the more impressive because the dollar has held firm over that period. Gold is priced in the U.S. currency, so its price tends to rise when the greenback falls and vice versa.

Gold is fairly expensive to store, but these days investors have to pay to store money in some safe government debt, and a recession would force official interest rates, some of which are already below zero, even lower.

The threat of currency wars makes the outlays appear even more worthwhile. Fractiousness over trade seems to be bringing an end to an era of worldwide restraint about overt beggar-thy-neighbour currency devaluations. It is becoming fashionable again to talk about fighting against the export-damaging effects of a rising currency.

President Donald Trump changed the tone in July, when he declared that China and Europe were manipulating their currencies and that the United States should match them. He may grow more irked. Japan's vice finance minister for international affairs, Yoshiki Takeuchi, earlier this month signalled Tokyo was ready to intervene if needed while Swiss National Bank boss Thomas Jordan has suggested he could loosen monetary policy further.

By contrast, no one is trying to keep a lid on the gold's value. Central banks may even be happy if it rises: their purchases of the precious metal last year were the second highest annual total on record. Such buying may have something to do with a growing U.S. willingness to use the dollar's pre-eminence in the financial system to further its international political aims. But if holding gold brings windfalls in the values of reserve, the shiny stuff will be the safest refuge of all.