The prime minister’s condemnation of Donald Trump’s remarks about the war in Afghanistan are his strongest public criticisms of the president yet.
They come in a week where circumstances have led Sir Keir Starmer to conclude three times that it was necessary to publicly rebuke a man he has ploughed so much effort into building a strong relationship with.
I am told Sir Keir, on returning to Downing Street on Friday afternoon, saw it as essential to make his views clear in the most direct terms.
His tone and body language conveyed his anger, as did his words, in which he said what President Trump had said was “insulting and frankly appalling”.
The president had claimed that the Nato defence alliance, of which the UK is a member, had sent “some troops” to Afghanistan, but they “stayed a little back, a little off the front lines.”
The comments, which are factually inaccurate, have been widely seen as crass and deeply offensive.
Four hundred and fifty-seven British service personnel died in the conflict and many more suffered life changing injuries.
The prime minister’s team tell me Sir Keir sees standing up for and defending the armed forces as a first order duty of his role, as both those serving and those killed in conflict can’t speak publicly for themselves.
Sir Keir’s response to the president is the third time in five days he has had to reach a quick judgement on how to calibrate a public response in defending what he sees as first principles under attack from the White House.
The first came on Monday morning, with his case for the sanctity of the sovereignty of Greenland and a plea for “calm discussion”.
Within 24 hours, the president was lobbing around insults about the government’s deal over the Chagos Islands.
Little wonder, perhaps, that No 10 approached Prime Minister’s Questions on Wednesday with a sense that what he planned to say there wasn’t without risk.
His language and tone on the president’s then ambitions for Greenland hardened, as he said the UK “will not yield” to pressure from Washington.
While the prime minister’s interventions on Monday and Wednesday were seen by officials through the prism of diplomacy and the reaction they might provoke, his remarks on Friday were approached with a different mindset.
I’m told the judgement was more simple: it was categorically the right thing to do, the prime minister concluded, given the gravity of offence the president had caused.
If Sir Keir manages a moment over the weekend to reflect on the last seven days, you have to wonder if he may judge it was a turning point in his relationship with President Trump.
It is a relationship he prizes and cherishes. Plenty have praised him for pulling it off, others have criticised him for hugging a deeply controversial President too close.
His argument has long been a close relationship is in the national interest.
The question now is how typical weeks like the last one might become, if the president’s penchant for what many see as outrage, insult and provocation becomes ingrained.