Police are considering “every possible angle” including the use of proxies by a hostile state after five suspects were released on bail over the suspected terror plot near an RAF base.
Five British nationals were arrested on suspicion of explosives offences and terrorism on Sunday after three suspicious vans were found near RAF Fairford in Gloucestershire, which is used by the US.
It is understood the material found was not viable explosives, but police have stressed that the investigation is continuing.
Speaking outside Scotland Yard on Monday, the head of UK Counter Terrorism Policing, Assistant Commissioner Laurence Taylor, said: “Following extensive interviews and inquiries, the five men who were arrested are being released on police bail this afternoon.
“To be very clear, this does not mean that the investigation is over. They are subject to stringent conditions on their movement and contact with others. They absolutely remain under investigation as we explore multiple lines of inquiry.”
Acknowledging speculation over whether Iran was behind the plot, he said police are keeping an open mind, and one possibility could be proxies “either knowingly or unknowingly working on behalf of a foreign state”.
Iran, and other hostile states including Russia, has been known to use criminal proxies to carry out crimes on its behalf on UK soil.
Its London embassy earlier said it “categorically rejects and strongly condemns the recent unfounded and malicious speculations” of Iranian involvement.
Mr Taylor said: “I also know there is significant interest in whether the current geopolitical context has a bearing on this incident.
“At Counter Terrorism Policing, we are working within this context every single day and, at this stage, we are keeping an open mind in this investigation.
“We have, as you would expect, ensured that our protective security advice and posture remain commensurate to the threat.
“But be assured, we are considering this from every possible angle, including that this may be actively committed by proxies or individuals either knowingly or unknowingly working on behalf of a foreign state.
“To respond to incidents such as these, rapid mobilisation is necessary, as we cannot take the risk whilst assessing that threat.
“However, once we understand the threat more clearly, we seek to return affected communities to normality as quickly as possible.”
Prime Minister Andy Burnham held a Cobra meeting on Monday evening “to make sure we have the full picture”, he told LBC.
Afterwards, Defence Secretary Wes Streeting, speaking at the Labour Party conference in Liverpool, said “the police and the security services have done everything that they could and should have been doing rapidly to help contain this situation”.
He said: “We’re acutely aware that the events at RAF Fairford have caused considerable disruption to the local community and also wider public concern.
“What we can say at this stage is that the response of our policing, counter-terrorism policing and security services has been exemplary. The investigation remains ongoing.”
Mr Streeting added: “Those investigations remain live and I can reassure the public who will be interested and want further information of two things: the first is that those five individuals are under stringent bail conditions and, secondly, that we remain with a live investigation and keeping the situation constantly under review.”
Speaking in the Oval Office, US President Donald Trump said the alleged plot “might be” linked to Iran, and added: “I will tell you, I would have said ‘Don’t let them have bail’.
“I’m surprised that they released them. I wouldn’t have done that.”
But he repeated his praise of the UK police, saying: “They’ve been very good. They worked with us very closely. We know everything about them (the suspects). We would not have released them.”
Police hope to be able to reduce the size of the cordon in place near RAF Fairford later on Monday, where dozens of homes were evacuated as bomb disposal experts examined the vans.
The force said on Monday evening evacuated residents could return to their homes.
In a statement, temporary Chief Constable Maggie Blyth thanked the local community for their “continued support and assistance during what has been an unprecedented couple of days”.
She said Counter Terrorism Policing were leading the investigation, and urged people to “avoid speculation while these inquiries continue”.
The officer added: “The last 48 hours have thrown our usually quiet and peaceful communities under the spotlight of the international media.
“There have been some reports in the media that have raised questions about our response, and I want to reassure people we have responded appropriately and quickly to all calls that have been made to us.”
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, north-west London.
Gloucestershire Constabulary was initially alerted to three suspicious vans travelling towards RAF Fairford at 12.45am on Sunday, and it is unclear what action was taken in the hour that followed.
The local farmer who spotted the vans and a group of masked men initially called the Ministry of Defence Police, but there was no answer, so called 999 at 1.36am, and armed police arrived about 10 minutes later.
She said the police had “dropped the ball”, telling journalists: “Who knew that a farmer would have to roll their sleeves up and report the activity?”
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