Prime minister’s initial refusal to help US could constrain Britain’s ability to protect its nationals in the Gulf and reassure allies

Middle East crisis – live updates

Britain knew that the US was considering attacking Iran from the moment Donald Trump told protesters that “help is coming” in the middle of January. It was obvious to the world that the White House was serious when the Abraham Lincoln carrier strike group was sent to the Arabian Sea in late January.

But as Trump gradually built up his “massive armada”, reinforcing it with a second carrier strike group in mid-February, UK deployments were constrained and limited even though there was a recognition that it was likely allies and bases with British soldiers would be attacked in an Iranian retaliation.

In January, Ministry of Defence insiders said they understood that Trump was “giving himself options” – so he could attack Iran if nuclear negotiations were deemed to be failing. Qatar asked the UK to redeploy a joint RAF squadron from Coningsby, Lincolnshire to the country that month, reassurance if an attack on Iran escalated.