Just last month, Donald Trump and his family spent three days in the UK for a state visit ahead of his trip to Normandy to honour the 75th anniversary of the D-Day landings in the Second World War.
They attended a white tie banquet with the royal family at Buckingham Palace and memorial services at Portsmouth, and were gifted first edition Winston Churchill books and sliver jewellery boxes, with only the small matter of mass protests to risk endangering the "special relationship" between the old allies.
But over the weekend, The Mail on Sunday reported leaked comments made by Sir Kim Darroch, the British ambassador to the US, in which the top diplomat described the Trump administration as "inept" and "uniquely dysfunctional".
On Sunday, the president was asked about the story and told reporters in New Jersey, rather testily, that Darroch had "not served the UK well".
On Monday, with no action forthcoming to remove him, Trump was furious, lashing out not just at Sir Kim but also Theresa May and her handling of Brexit, which he has previously been much kinder about in person.
The idea that Darroch is "not well liked" is actually not true: Trump administration veterans Kellyanne Conway, Wilbur Ross, Sarah Huckabee Sanders, Sean Spicer and Reince Priebus are among those known to have attended the ambassador's lavish Washington receptions (no doubt he really spoiled them with Ferrero Rocher).
Responding, Downing Street insisted Sir Kim still had the prime minister's "full support" but added:
We have made clear to the US how unfortunate this leak is. The selective extracts leaked do not reflect the closeness of, and the esteem in which we hold, the relationship.
At the same time, we have also underlined the importance of ambassadors being able to provide honest, unvarnished assessments of the politics in their country.
Foreign secretary and Tory leadership contender Jeremy Hunt - whom the leaker may have intended to personally embarrass by passing the offending memo to a newspaper known to back his rival, Boris Johnson - said he did not approve of the sentiment but stressed the necessity of ambassadors speaking freely, even if they have "frank views" to express.
Neither reaction was exactly the strong condemnation Trump was expecting and Sir Kim duly had his invitation to a White House dinner for the Emir of Qatar rescinded (one man who was on the guest list was Robert Kraft, the owner of the New England Patriots who was embroiled in a prostitution scandal earlier this year).
Unappeased, Trump was even angrier on Tuesday.
This is vintage stuff from The Donald.
Not even London mayor Sadiq Khan, whom he denounced as a "stone cold loser", got called "wacky", "a very stupid guy" or a "pompous fool".
As for Brexit and Trump's much boasted-of business acumen - how did it work out getting Mexico to pay for that border wall sir?