The suspected bomb plot targeting RAF Fairford was foiled after one of the suspects made a call to police an hour before their arrest, it has emerged.
One of the suspects is understood to have called police early on Sunday before he and four others were arrested on suspicion of explosives and terrorist offences. They were all released on bail on Monday.
Police are now looking into whether the men, who are all British nationals, were acting as proxies for Iran, according to The Times. They are said to be probing whether the caller got cold feet or whether it was part of the plan.
The Independent has approached the Met Police for comment.
Officers discovered a quantity of petrol but no explosive devices in the three vans that sparked the major security alert near the Gloucestershire base being used by the US. Police had received a call from a farmer relating to “suspicious vehicles” travelling towards the base at 1.36am on Sunday.
On Tuesday evening, US president Donald Trump said he was “disappointed” at the decision to grant the five men bail.
He said: “We were involved in (the investigation), but as you know, your fellow countrymen, let them go.
“Well, they didn’t let them go. They put them out on bail. I assume they haven’t watched closely… they should not have done that.”
The head of UK counterterrorism, Policing Assistant Commissioner Laurence Taylor, said the decision to release the suspects on bail was an investigative decision.
Speaking outside New Scotland Yard, he confirmed on Tuesday that no improvised explosive devices had been found within the vans.
“A police response was activated in the early hours of Sunday morning due to a range of information that we received,” he said. “This included a call from the member of public about several vehicles acting suspiciously close to RAF Fairford.
“Now, those vehicles, as I explained yesterday, have been subject to extensive examination, with the support of military assets and forensic experts, and we can confirm that no improvised explosive devices have been found.
“We have found a quantity of an accelerant, petrol, and we have recovered that as part of our investigation.”
He added the five suspects released “remain under investigation” and “must adhere to strict conditions” as the probe continues. “The safety of the public is at the forefront of our investigative decision-making, and this was certainly the case yesterday,” he said.
“I understand why this development will have come as a surprise to many, but I’d like to reiterate that it was an investigative decision, and one which is grounded in experience and careful consideration of policing powers.”
The five suspects are a 24-year-old from Camden, north London; three men aged 23, 24 and 25 from Westminster, central London, and one aged 24 from Willesden, northwest London.
Villagers living near RAF Fairford in Gloucestershire, dozens of whom were dramatically evacuated from their homes on Sunday morning, were slowly returning to normal on Tuesday. Police cordons are expected to be fully lifted on Wednesday.
Questions over Iran’s potential involvement in the attack have continued as US secretary of state Marco Rubio claimed in a television interview that the suspected plot “clearly involves the hand of a foreign actor”.
Speaking to Fox News, Mr Rubio said: “It’s one that clearly involves the hand of a foreign actor. I won’t get into great detail about that yet.
“I do want to thank the authorities in the United Kingdom who have been very co-operative and on top of it.”
He added: “I know a lot of people are disturbed by the news that some of these people have been released on bail, as some of the people are being investigated, and obviously we’re engaging with them on all of that.
“Beyond that, I would argue that they’ve been very co-operative and very helpful on something that’s a very serious incident.”
Iran’s embassy in London has strongly denied any involvement in the alleged plot.
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