If something cannot go on forever, it will stop. The question is how long that will take with Donald Trump. It is little use speculating about the next four years. Just multiply Mr Trump’s first four weeks and ask how long America’s system can take the strain.

In his first month Mr Trump has declared war on the intelligence agencies and the media. It looks like the judicial branch is next on his list of enemies. There is no middle ground in Mr Trump’s Washington. Either the forces that are against the president will bring him down or he will destroy the system. My bet is on the first. But I would not stake my life on it.

Do not be reassured by Mr Trump’s cabinet. Many of them are experienced individuals. James Mattis, the secretary of defence, Rex Tillerson, secretary of state, and Steven Mnuchin, the nominee for Treasury secretary, are professionals. We may dispute their priorities but we have no basis to contest their hold on reality.