The prime minister wants to keep everyone happy. He has been loath to criticize Trump, has warmed up Britain’s post-Brexit partnership with the European Union, avowedly backed Kyiv and thawed ties with China. At a time of geopolitical upheaval, he is attempting to squeeze Britain into an impossibly tight Venn diagram.

If there is a cease-fire without a backstop, it will simply give him the opportunity to wait and to come again,” Keir Starmer warned on the flight to Washington, D.C.

But Donald Trump has already suggested he is reluctant to do this. Speaking hours before Sir Keir was due to arrive in Washington, the US President said: "I'm not going to make security guarantees beyond very much," Trump told reporters as he hosted his first cabinet meeting of his second term.