There is not much that can unify benighted Brexit Britain at the moment, but Donald Trump’s thoughtless retweeting of three hate videos from the deputy leader of a tiny fascist group has brought together left and right in an unlikely chorus of condemnation, including a rare public admonishment from 10 Downing Street. Trump couldn’t let that go and pushed back overnight. “Don’t focus on me, focus on the destructive Radical Islamic Terrorism that is taking place within the United Kingdom,” he tweeted. “We are doing just fine!”

With Britain looking increasingly isolated in Europe, and desperate for a deal with the United States to replace its trade with the European Union, the Tory Prime Minister Theresa May might have been expected to guard the “special relationship” and make no further comment. But that was not to be. The first evidence of her unbending stand came from her close ally in the House of Commons, Home Secretary Amber Rudd, when she repeated that it was wrong for Trump to retweet videos. A few hours later, May, who is on a tour of the Middle East, stood by her original criticism.

This universal denunciation of an American president is unprecedented in Britain, and while the Home Secretary insisted in the Commons that the invitation for a state visit had been issued (and accepted), she said no date was set. Indeed, it seems increasingly unlikely that Trump will ever be the guest of the Queen and be treated to the full panoply of British pomp, which would include an address to the Houses of Parliament. Some Labour opposition M.P.s are even calling for him to be arrested the moment he sets foot on British soil for the offense of inciting racial hatred. But the challenge of protecting the president in the face of mass demonstrations that have been promised is probably enough to deter the White House from taking up the invitation.

There is also the delicate problem of the Royal wedding next year. While the Obamas, who are friendly with Prince Harry, seem certain to be invited to his nuptials with the American actress Meghan Markle, it is hard to see the president and the First Lady attending the ceremony in Westminster Abbey. In the past, the president’s attendance would be a natural manifestation of the special relationship, but today, that looks as improbable as the state visit.

The special relationship is mostly a British vanity; the majority of Americans, after all, have no idea that such a thing exists. But the bonds between the two countries are deep, with their political establishments working closely on surveillance and security operations and in military and diplomatic matters. Under more normal circumstances, you would expect the British ambassador to the U.S., Sir Kim Darroch, to be moving in the background, reassuring the administration that everything was going to be all right. Instead, he formally raised the British government’s concerns with the White House, so no one could doubt Britain’s anger.

Anyone who deals with Trump is faced with the question, “Is he sinister, or just plain dumb?” In this case, it seems like it could be both. To his 43.7 million Twitter followers, he promoted Jayda Fransen, the deputy leader of the fascist Britain First party, who was recently convicted of religiously aggravated harassment in one case, and is currently facing trial for the same charge in another. The unthinkable equivalent would be for May to endorse the Klan and then get nasty about it when the American government objected.