Steven Mnuchin was having a tough day. For several months the Treasury secretary had tried to co-ordinate the US side in trade negotiations with China. But on May 29, he found himself explaining to Liu He, the Chinese vice-premier, why President Donald Trump had just reneged on a deal aimed at preventing a trade war.

Two weeks earlier, Mr Mnuchin hosted Mr Liu at Café Milano, a Georgetown restaurant popular among Washington’s diplomatic corps and Trump officials. Four days after the dinner, Mr Mnuchin announced that the threatened trade war was now “on hold” and that the US would not place tariffs on $50bn of Chinese goods.

Yet, as he returned to work after the Memorial day weekend, he was met with the news that Mr Trump had resurrected the tariffs. In a stark example of how the president can blindside his officials, Mr Mnuchin had been told the announcement would come the next day, according to a senior official.