The “special relationship” between the US and UK has lurched from cordiality to open criticism since Donald Trump entered the White House.
The US president again risked inflaming tensions with one of his country’s closest allies by deriding the NHS as “broke and not working”.
He rarely minces his words about UK affairs, a habit which has posed a diplomatic headache for Theresa May as she seeks to forge stronger relations with Brexit looming.
Here are the key moments of his premiership:
2016
November
Mr Trump is elected as president of the United States, forcing UK politicians to quickly change tack in their handling of the billionaire businessman.
Prime Minister Mrs May congratulates Mr Trump on his victory and says Britain and America will remain “strong and close partners”.
Nigel Farage, the former Ukip leader of whom Mr Trump is an admirer, embarrasses Mrs May by beating her to a meeting with the new president.
2017
January
The Prime Minister becomes the first world leader to meet the president following his inauguration.
She faces criticism for offering President Trump a state visit just seven days into his presidency.
But they are photographed holding hands outside the White House, and Mrs May gets a significant commitment from the president to Nato.
Mrs May’s spokesman says she does “not agree” with Mr Trump’s refugee ban, an executive order signed just hours after their meeting, and will make representations if it affects Britons.
February
Cracks begin to appear in the relationship when Mrs May eventually denounces Mr Trump’s travel restrictions on Muslims as “divisive and wrong”, echoing statements from her ministers.
And she reportedly pokes fun at the size of Mr Trump’s hands, telling a Conservative fundraising party in response to applause from donors: “Thank you very much for that wonderful reception.
“I don’t think I have received such a big hand since I walked down the colonnade at the White House.”
March
Mrs May’s spokesman denounces “ridiculous” allegations made by the White House press secretary that GCHQ spied on Mr Trump before the presidential election. The president refuses to give a public apology.
May
The PM rebukes Mr Trump after intelligence shared with the US in the wake of the Manchester terror attack is leaked to American media.
Mr Trump later describes the PM as “very angry” about the leaks, which prompted British police to temporarily suspend sharing information across the Atlantic, and promises to investigate.
June
In a bad month for relations, the Prime Minister tells Mr Trump of her “disappointment” at his decision to pull America out of the Paris Accord on climate change.
She then directly condemns Mr Trump’s attacks on Sadiq Khan’s handling of the London Bridge terror attack as “wrong”.
September
Mrs May delivers a rebuke to the US president after he claimed the Parsons Green Tube bomber was “in the sights” of Scotland Yard. The Prime Minister said: “I never think it’s helpful for anybody to speculate on what is an ongoing investigation.”
November
Mrs May and Mr Trump fall out spectacularly over his retweeting of anti-Muslim videos posted online by the deputy leader of the far-right Britain First group, Jayda Fransen.
The PM said Mr Trump was “wrong” to retweet the videos, and the US president hits back at Mrs May on Twitter by telling her to focus on “destructive radical Islamic terrorism” in the UK, rather than on him.
2018
January
The US president says he has cancelled plans to travel to the UK to open the new American embassy, hitting out at the location of the project.
Later in the month, Trump blows hot and cold with the Prime Minister during a trip to the World Economic Forum meeting in Davos.
Following talks with Mrs May, the president appears keen to clear the air about tensions between the two nations, declaring: “We love your country.”
But then, in an interview with Piers Morgan, he pours scorn on Britain’s approach to Brexit negotiations and says he would take a “tougher” approach with Brussels.
February
Mr Trump uses the NHS as an example of why universal health care should not reach US shores.