The unexpected mass withdrawal of America’s heavy bombers happened so suddenly on Sunday that it has got everyone wondering what prompted it.

An “abundance of caution,” says US Vice-President JD Vance, adding that Washington felt Iran was doing what it has “done for 49 years… which is engage in acts of terrorism against the US and against a lot of other people”.

An abundance of panic is how others have seen it.

For the last seven months, America’s B-1 Lancer bombers and other aircraft have been operating out of Fairford to strike the Iranian missile launch sites.

In July, Iran threatened any country that provided the US with such a facility would be considered a “legitimate target”.

Then on 27 September, a major incident was declared when five British men were arrested and later bailed after being seen acting suspiciously with their three white vans in the dead of night close to the airbase perimeter.

At the weekend, a UK-Iranian dual national was arrested on suspicion of preparation of terrorist acts. He was also released on bail.

Twelve valuable and strategically important B-1 bombers have now departed en masse and seemingly in such a rush that, reportedly, the air-to-air refuelling aircraft needed to get them back across the Atlantic to their home bases in the continental US were still being fuelled up while the B-1 Lancer crews were being ordered to scramble to take off.

So something was considered urgent and dangerous enough to prompt this.

It was almost certainly a fresh piece of intelligence, whether true or not.

British officials would not reveal what it was, but they did say “there is an ongoing high tempo of threat from Iran to the UK, and it is logical that US airbases would be pretty high on any targeting list”.

Iran has denied any connection with events at RAF Fairford. The US Secretary of State Marco Rubio has also played down any suggested link between this rushed evacuation and the arrests made on 27 September.

The context here is that while the UK is not at war with Iran, the US is – and that is a distinction Tehran has publicly challenged. As far as the Islamic Revolution Guards Corps is concerned, Britain is already a participant in America’s war with Iran.

There is also a cost factor involved here.

The B-1 Lancer bombers which have now left each cost about $330 million.

The Americans have already suffered heavy financial losses from Iranian strikes on US bases in the Middle East.

In late March the Iranians hit Prince Sultan Air Base in Saudi Arabia, destroying an E-3 Sentry AWACS early warning plane.

That aircraft alone cost over half a billion dollars.

General Sir Richard Barrons, who served in one of the highest ranks in the British Armed Forces, said: “We now live in a world where a £1,000 drone could wreck one of those aircraft.

“So, I don’t know what the threat was but the most prudent thing to do would be to remove them to Texas given that they were not doing very much at the minute”

But how does the US ordering the bombers to leave RAF Fairford reflect on Washington’s confidence in the ability of the UK to keep the base secure?

Britain remains an incredibly close ally of the US and there are still hundreds of American servicemen and women stationed at RAF Fairford, as well as at other bases at Mildenhall and Lakenheath.

Work will likely be ongoing in secret now to review security at the base on both sides of the perimeter fence.

But it is hard not to conclude that, despite efforts to play down the drama, this is an embarrassing episode for the UK.

Rubio said the US has “confidence in the security of all our bases” and said the administrations was working “very closely” with UK authorities, who “couldn’t be more cooperative”.

UK counter-terrorism police are still investigating what happened at RAF Fairford and are keeping an open mind as to what exactly was behind events there.

I have been told a large amount of data, CCTV and other information is still being trawled through while the men remain on bail.

Meanwhile, now that the bombers have left British soil, the US insists it can still deploy them from its domestic bases anywhere in the world.

That could be seen as putting a brave face on something which, for Iran, sees a major US strike force effectively driven back to its home base in the continental United States.