Trump tests the special relationship between UK and US
US President angers the UK again with anti-Muslim tweets, but friendship will hold because both nations need each other
British Prime Minister Theresa May's temptation must have been to counterpunch after receiving Mr Donald Trump's advice to concentrate her mind on the Islamist threat to Britain rather than react to his retweeting of British far-right anti-Islam videos.
"@theresamay, don't focus on me, focus on the destructive Radical Islamic Terrorism that is taking place within the United Kingdom," the US President tweeted to his 40 million-plus followers.
"Two of America's worst mass shootings (Las Vegas concert and Texas church) happened on your watch," she might have tweeted back.
"Shouldn't Potus (President of the United States) focus on gun laws?"
She didn't do that, of course.
Her actual response was brusque.
"It is wrong for the President to have done this," she concluded - a comment within the bounds of diplomatic protocol. What one frank friend might say to another.
The question which arises from this: Is the UK-US friendship, the "special relationship," special any longer?
Education Secretary Justine Greening told the BBC that while she didn't agree with Mr Trump's tweets, she "did not believe it should detract from the close relationship the UK has had for many, many years and will go on to have with America and the American people".
In the short term, however, the relationship will tremble. As will Mrs May, for she more than any other Western leader sought a demonstrative friendship with Mr Trump, who held her hand in the White House Rose Garden.
For Mrs May, a trade deal with the US is a necessity after/if Brexit takes the UK out of the European Union's single market.
There is a greater dependence than usual on the UK side of the relationship, one of which Mr Trump will be well aware. And Mrs May will have been aware that he is aware.
Nonetheless, she still issued a public rebuke - a sign of her disgust, of her realisation that the British establishment and most of its population would share her disgust and that she sees some things as too important to remain silent.
Yet if Britain is dependent - as all European states are on the US military umbrella, among much else - so is America dependent on Britain.
The "special relationship" is more treasured by British politicians than most American ones, but it still matters, especially when Washington seeks allies in controversial projects such as the Iraq invasion.
For Mr Trump to prioritise the desire to hit back at the British leader over the threat of damage to that relationship is to reveal the terrible shallowness of his grasp of international relationships, and to rouse yet again fears that his unpredictability and narcissism threatens us all.
If any good came of the latest fine mess Mr Trump has got the presidency into, it is that it has, for at least a day, brought the fractured and fractious British politics together behind Mrs May.
Mr Sadiq Khan, the Labour (and Muslim) Mayor of London, himself a target of Mr Trump's earlier tweets, said that the President's comments were "a betrayal of the special relationship".
Certainly, some of Mr Trump's right-wing supporters appreciate his bluntness about Islamic extremists.
"That is not news," Mr Mark Krikorian, a supporter of the President and executive director of the anti-immigration Centre for Immigration Studies told the New York Times of Mr Trump's Twitter sharing. Mr Trump "just expresses that stuff in the most unfiltered, guy-ranting-in-the-bar" way.
It isn't that.
Mr Trump's "style", in this context, is directly and repeatedly anti-Muslim. He has sought and still seeks to stop Muslims enteringthe US.
He said, falsely, that thousands of people in New Jersey - "a heavy Arab population" - had been shown on TV cheering after the planes destroyed the twin towers of the World Trade Centre on 9/11.
The unverified videos he re-tweeted this week came from the Britain First group, not just far right but dedicated to stirring up violent action against Muslims.
Compare Mr Trump's response with his recent predecessors.
Mr George W. Bush had to bear the shock of the 2001 attacks as a newish president, but took some care in his reaction to the horror to tell Muslims that he respected the "good and peaceful" teachings of Islam and that America's enemy was "a radical network of terrorists", not "our many Muslim friends".
Mr Barack Obama continued that tradition.
In the UK, as in other Western democracies, that distinction between the large majority of peaceful citizens of Muslim faith and the few deadly, militant Islamists among their number is maintained.
How else could a civil society be retained if thousands, in some countries millions, of citizens and would-be citizens were demonised and made the butt of violent prejudice?
Mr Trump's behaviour shows how little he understands this.
Washington and Westminster may continue their close alliance, but the Mr Trump should not see his decision to give publicity to a semi-fascist group's efforts to sow violent hatred - then capping that with the need to humiliate a close ally - as a good day's work. - REUTERS
The writer co-founded the Reuters Institute for the Study of Journalism at the University of Oxford, where he is senior research fellow.