The alleged bomb plot near an RAF base was uncovered after one of the suspects called police himself, it has emerged.
One of the five men arrested near RAF Fairford in Gloucestershire during the early hours of Sunday reportedly dialled 999.
Armed officers raced to the scene and detained the group. The suspects were made to remove their tops amid fears they could be wearing suicide vests.
A farmer who encountered three suspicious vans blocking a rural road said she saw “eight to 10 masked men” moving through woodland and across nearby fields. It is now understood that the figures she saw in the darkness were armed police officers.
Investigators are examining why one of the suspects contacted 999. They are considering whether he was attempting to withdraw from the alleged plan or whether the call formed part of a wider strategy.
One line of inquiry is whether the incident, which is allegedly linked to Iran, was not a genuine attempt to carry out an attack but instead a stunt or “calling card” intended to send a message to British and US authorities.
Residents were evacuated from their homes on Sunday morning as elite SAS troops were deployed to the base and a major incident was declared.
However, questions were raised after the five men, aged between 23 and 25, were released on bail within 36 hours of the arrests.
Counter-terrorism police said on Tuesday that no explosive devices had been found in the vans abandoned by the suspects, although officers recovered a “quantity of petrol”.
Counter-terrorism police are continuing their investigation after petrol was found in vans discovered near RAF Fairford
Police pictured arresting five men on terror charges near RAF Fairford in Gloucestershire. All five are British men from London and in their 20s, police said, and they have since been released on bail
Assistant Commissioner Laurence Taylor, head of UK Counter Terrorism Policing, said releasing the suspects on bail was an “investigative decision”. He stressed that protecting the public had remained at the “forefront” of the operation.
Speaking outside Scotland Yard, Assistant Commissioner Taylor 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.”
He added: “A police response was activated in the early hours of Sunday morning due to a range of information that we received.
“This included a call from a member of the public about several vehicles acting suspiciously close to RAF Fairford.
“Those vehicles have been subject to extensive examination, with the support of military assets and forensic experts, and we can confirm that no improvised explosive devices were found. However, a quantity of petrol was recovered.”
Detectives will now have to assess whether the men’s alleged conduct meets the threshold for offences under the National Security Act, The Times reported.
The suspects could face up to 14 years in prison if they are found to have plotted an attack on Iran’s behalf, even if they say they were unaware they were acting for the Middle Eastern country.
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RAF Fairford has previously been used by the US military to conduct strikes against Iran.
The suspects include a 24-year-old man from Camden in north London, along with a 23-year-old, two 24-year-olds and a 25-year-old, all from Westminster in central London.
Police would not confirm when they are due to answer bail.
On Monday, residents from around 85 evacuated households were allowed to return home.
One local businesswoman complained the arrested men had been bailed and potentially allowed back to their homes before local residents in Whelford had.
Police cordons near the base are expected to be completely lifted on Wednesday, and searches of the London homes of the five suspects have been completed.
On Tuesday, US Secretary of State Marco Rubio insisted the plot ‘involved the hand of a foreign actor’.
In a television interview, Mr Rubio mentioned Iran by name, noting that the regime had previously threatened to target US interests. However, he stopped short of directly blaming Tehran for the incident.
Potential involvement by Iran was understood to be one line of inquiry for British investigators, and the nation has used proxies in the past to carry out acts in the UK.
However, Tehran ‘categorically’ denied any involvement in the alleged plot in Gloucestershire.
In a statement, its London embassy dismissed reports linking Tehran to the arrests as ‘unfounded and malicious speculations’.
The embassy added: ‘The circulation of such fabricated speculations, particularly in the aftermath of the criminal acts of aggression committed by the United States and the Israeli regime against the Iranian people, will serve no purpose other than to fuel Iranophobia propaganda in the UK.
‘The Islamic Republic of Iran reserves the right to take appropriate legal measures, as necessary, to safeguard the rights and interests of the country and its people in response to misleading and damaging media narratives.’
Police officers guard an area as roadblocks remain in place near RAF Fairford airbase, after police declared a major incident at the base
Mr Rubio described the events near RAF Fairford as a ‘very serious situation’ and thanked British authorities for their response, saying they had been ‘very cooperative and very helpful’.
He added that ‘a lot of people are disturbed’ by the decision to grant bail to the five suspects.
Assistant Commissioner Taylor said the worries felt by people over a suspected terror plot near RAF Fairford have been ‘heightened by the international commentary’.
