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It is unsurprising that Iran considers the UK bases used by US bombers to attack the country – RAF Fairford in Gloucestershire and Diego Garcia in the Indian Ocean – to be “legitimate targets”.

Such threats might have been dismissed in the past as unrealistic bombast, but in a year when warfare in the Gulf and Ukraine has been dominated by drones, along with cruise and ballistic missiles, nations that once believed themselves safe have suddenly become vulnerable. Iran fired two missiles at Diego Garcia in March which failed in flight or were shot down, but the Iranians clearly believed they had the range to reach the island. Diego Garcia is 2,350 miles from Tehran, while London is 2,750 miles away.

Seeking to balance between not offending Donald Trump and refusing to join more fully in his war on Iran, Britain has made a fine distinction between “defensive” US bombing missions, which are allowed, and “offensive” ones, which are not. But since Iran sees itself as the victim of an unprovoked attack by the US and Israel on 28 February, the British argument about the US defending itself and its allies is unlikely to impress the Iranians.