Three years ago, Donald Trump stood before a group of white-gloved — and mostly white — police officers on Long Island, and offered a bit of professional advice.

“Please don’t be too nice!” the self-described law-and-order president implored, as the officers whooped in delight.

After the police killing of George Floyd, a black man, in Minneapolis unleashed America’s worst civil unrest in half a century, Mr Trump this week showed no sign of reconsidering his attitude to policing. Governors should “dominate” protesters, the president declared, as he agitated to send the military on to America’s streets.