‘The Special Relationship only exists when the Americans want something,’ a former Downing Street aide observed after Donald Trump rejected the Chagos Islands deal. There are profound differences between London and Washington over military action against Iran while the fourth anniversary of the war in Ukraine this week has exposed further fault lines. The result is that Anglo-American relations are at their worst point since the general election.

Starmer’s team argues he should not be ousted at a time of huge international instability. But the reality of the Anglo-American relationship raises three questions. Where did things go wrong? Does the PM still have some kind of relationship with Trump? And would it matter if he were replaced by Angela Rayner, Wes Streeting or anyone else?

The PM apparently hates the way Trump calls him at random when he is with his family

During the first 18 months of his premiership, it became accepted, correctly I think, that one of the few areas where Starmer excelled was foreign affairs. He seemed particularly good at handling the often capricious President. But it is also true that the two great cleavages of recent weeks – Iran and Chagos – are intimately tied to Starmer’s personal fetish for subordinating the sovereignty of parliament to international law.

If the Prime Minister believes in anything, it is that the web of international treaties constructed to constrain rogue states after the second world war overrides domestic law. His appointment of Richard Hermer as his Attorney General was proof that this would form the backbone of his premiership.

Hermer’s numerous legal opinions flow from this belief in the primacy of international law: that Britain must not support an American attack on Tehran and must not allow America to use British air bases for the attacks. This is what prompted Trump to change his mind on the Chagos deal, by which Britain would cede control of the islands to Mauritius and then lease back British airbases which America also uses.

My understanding is that the US has not made a specific request to use the base for an Iranian operation, nor has the UK explicitly rejected the idea. However, ‘general soundings’ have made clear what the answer would be. Insiders say that Starmer and Hermer’s approach is no different from what any other PM would do. The belief in government is that allowing the US to use our bases without legal backing ‘smells like Iraq’.

This has outraged Team Trump. ‘It’s just not how they roll,’ says one insider who has dealt with the Americans. ‘Their risk spectrum is significantly different. International law, due legal process – they don’t give a shit about that.’ Privately there have been threats that the US will not be there in Britain’s hour of need. The Iran decision led directly to Trump pulling the plug on Chagos. Those who deal with the Trumpies say there is no point ‘continually making the same argument’ and the deal is now ‘in the medium-length grass’.

However, by far the bigger issue is Ukraine and that is where Starmer has deployed most of his capital with Trump. The President and his envoy Steve Witkoff began with a fundamentally misguided understanding of the conflict. ‘All of them basically come back to this belief that it’s about territory, that peace is a real estate deal,’ one insider said. On calls with British officials, Witkoff openly ridiculed the French for saying ‘root causes’ were behind Vladimir Putin’s invasion. ‘He would mock the idea that if there’s peace, the Russians will just rearm and be a threat to Europe.’

The view of Britain’s political and military leaders is quite different after four years of working closely with the Ukrainians. ‘There is a whole generation of Europeans who have made the trip to Kyiv and it feels like the most meaningful thing they’re doing in their political careers,’ a diplomat says.

The key achievement of the Starmer government, in this telling, is that ‘we have persuaded the Americans to listen to us’. A senior adviser says: ‘People are saying that Starmer’s foreign policy is a failure because of Chagos. But if you look at Ukraine, it’s been a success.’

Intercepted phone calls and messages from senior Russians ridiculing Trump have been shared by the British with the Americans. ‘We have continually shown them intelligence that shows the Russians are lying,’ a senior security source revealed. ‘The Russians are privately mocking Trump over his naivety about Putin’s intentions. Putin doesn’t want to end the war.’

Yvette Cooper, the new Foreign Secretary, spent an hour last week with Marco Rubio, US Secretary of State. But the four key relationships that have moved the dial are Starmer and Trump; David Lammy and Vice President J.D. Vance; the US embassy in Washington, which enjoys closer ties to the White House than any other D.C. diplomats; and, most important, Jonathan Powell, the national security adviser, and Witkoff.

Henry Kissinger is said to have asked: ‘Who do I call if I want to call Europe?’ Now a senior member of the Trump administration refers to Powell as ‘dean of the European national security advisers’. A Foreign Office source concludes that if there is regime change in London: ‘The one relationship I fear might be irreplaceable is Jonathan Powell and Witkoff.’

Opinions are divided about whether Starmer’s departure would make any difference. The PM apparently hates the way Trump calls him at random when he is with his family but he has built a ‘load-bearing relationship’ with the President. This is based, in part, on the fact that both have lost brothers. In their first meal together, Trump interrupted a conversation about tariffs to ask if Starmer’s brother had ‘a good death’, genuinely troubled by his loss.

But those who want Starmer gone will agree with the official who says: ‘Trump’s mum was British. He loves the UK and he views having a great relationship with the PM as part of his job.’

Diplomats doubt that any new leader would be given the same space by Labour MPs to develop ties with Trump. But that is another reason why foreign policy will not save Starmer. As one MP puts it: ‘If Keir thinks sucking up to Trump is the argument which saves him, he is going to be in for a rude shock.’