Diplomatic tightrope on Iran just got more precarious for Starmer

Sir Keir Starmer has been treading a delicate diplomatic tightrope all week on the issue of Iran.

Last night's airstrikes by the US mean the challenges facing the prime minister could now continue for months.

Sir Keir's repeated calls for de-escalation have clearly not been heeded by the White House.

Yet he has avoided direct UK involvement in military action and has sought to maintain what British diplomats claim is a solid and valuable relationship with US president Donald Trump.

The response from ministers appears to be it was not the means they wanted, but they supported the outcome.

The UK has not explicitly endorsed the method, but the result - a delay in Iran getting nuclear weapons - is, they argue, in the UK's national interest.

Sir Keir's position has shifted since Tuesday, when he seemed confident Trump would not intervene, after sitting next to him at a G7 dinner in Canada.

"I was sitting right next to President Trump, so I've no doubt, in my mind, the level of agreement there was," he said.

Just four days later the president intervened. Did the prime minister misread Trump? Or did the president - whose unpredictability is central to his foreign policy approach - just change his mind?

No 10 has told us it was given advanced warning of the US action, but the UK was not asked to take part. We do not know why.

There had been speculation that US B-2 stealth bombers could have used the UK's Diego Garcia airbase in the Indian Ocean as a waypoint en route to Iran.

Instead, "Operation Midnight Hammer" involved B-2s flying non-stop for 18 hours from Missouri to reach their targets, according to the Pentagon.

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It is possible the UK was not asked for assistance because it would have been a difficult request to grant.

There have been debates at the top of government in recent days about the legality of any UK involvement, with the attorney general, Lord Hermer, providing advice on a range of scenarios.

With the next steps in the conflict unclear, the US could end up requesting military support from the UK in the coming weeks - prompting further difficult decisions for the prime minister.

US defence secretary Pete Hegseth has responded to concerns the US attacks could prompt the start of a long conflict by insisting: "This is most certainly not open-ended".

Yet the actions of both the The Foreign, Commonwealth and Development Office (FCDO) and the Ministry of Defence (MoD) suggest they fear retaliation from Iran.

This is why British diplomats have been planning a flight early next week to help "vulnerable British nationals and their dependents wanting to leave Israel and the Occupied Palestinian Territories".

Defence sources have told me measures to protect British armed forces in the Middle East have been strengthened in the past few hours, with additional fighter jets already in the region and at "high readiness".

One UK diplomat told me UK-US relations remain strong, as demonstrated by Foreign Secretary David Lammy's long meeting with secretary of state Marco Rubio and Middle East envoy Steve Witkoff on Friday.

Another senior government source said: "We know how to support [our allies] without encroaching on legal ground."

However, we do not know if - or how - Iran might respond, or whether the UK or its military could be targeted. Starmer's high-wire act has just become even more dangerous.