In early 2018, before an audience of chief executives and politicians at Davos, Steven Mnuchin got in trouble for saying the obvious: a weaker dollar would help US manufacturers export their products.

Mr Mnuchin, the US Treasury secretary, had cast a sliver of doubt on a policy held by administrations of both parties for over two decades, namely that when markets want the dollar to strengthen, the Treasury should stand by and allow it to. And so, like other Treasury secretaries before him, he was forced to clarify, confirming his commitment to a strong dollar.

On Monday, Mr Mnuchin was finally allowed to speak freely, declaring that China manipulates its currency to create an unfair competitive advantage, with the implication that the greenback is overvalued against the renminbi. The US Treasury is no longer bound by verbal rules of the strong-dollar policy.