In a world where financial transactions ping around the world in a fraction of a second, the booming triangular trade underscores the gold market’s reliance on lumps of metal. In normal times, claims on billions of dollars of gold are traded without the bars ever leaving a vault.

But the distortions created by Trump’s radical trade policies have strained the system. Even though Trump has never mentioned bullion tariffs, the slight chance that he might do so was enough to send the price of gold futures in the US higher than in London, creating an arbitrage opportunity for traders willing to transport the metal across the Atlantic.