A dual UK-Iranian national has been arrested as detectives investigating suspected terrorist activity near RAF Fairford widen their investigation.

The 27-year-old man was arrested in Westminster, London, on Thursday on suspicion of preparation of terrorist acts under Section 5 of the Terrorism Act 2006.

Counter Terrorism Policing said officers also searched two properties in Westminster as part of the investigation.

A second man, aged 26 and a UK national, has been questioned under caution.

The development follows the arrests of five British men in their 20s near the Gloucestershire airbase during the early hours of Sunday, September 27.

All five have since been released on police bail and remain under investigation.

Petrol recovered from three vans

The original arrests followed a major emergency operation involving three vans near RAF Fairford.

Armed police attended the area, and around 85 households in nearby Whelford were evacuated while specialist teams examined the vehicles.

No improvised explosive devices were subsequently discovered.

Police did, however, recover a quantity of petrol from the vans.

The purpose of the petrol has not been established publicly, and investigators have not confirmed claims surrounding what the men may have intended to do.

Counter-terrorism investigation ‘hugely complex’

Senior National Coordinator for Counter Terrorism Policing Vicki Evans said detectives are continuing to examine a number of possible explanations for the activity.

She said: “The investigation into circumstances surrounding events in Gloucestershire is hugely complex, and our specialist teams are interrogating multiple lines of enquiry.

“As we’ve made clear, we’re looking at all possible angles – including possible foreign state involvement.”

The arrest of a dual UK-Iranian national does not establish that Iran or any other foreign government was involved.

Police have not announced any confirmed foreign-state connection and say the investigation remains open-minded.

Questions remain over how the incident unfolded

There are also continuing questions surrounding the circumstances which first brought police to the area.

Reports suggest one of the original suspects contacted the emergency services before the arrests took place. The reason for that call has not been publicly explained.

Separately, a local resident has described encountering a group of masked men and three white vans near Whelford before calling 999.

The woman has said she initially attempted to contact RAF Fairford and then 101 before eventually getting through to emergency services.

Police have not publicly established whether everyone reportedly seen by the witness was connected to the five men subsequently arrested.

Netanyahu claims Israel provided intelligence

The investigation has also attracted international attention after Israeli Prime Minister Benjamin Netanyahu claimed Israel had provided Britain with intelligence concerning what he described as an “Iranian-sponsored attack”.

British counter-terrorism investigators have not publicly confirmed that Israeli intelligence led to the RAF Fairford operation or established that the incident was directed by Iran.

Investigators have confirmed only that possible foreign-state involvement is among the lines of enquiry being examined.

RAF Fairford is used extensively by the United States military, including as a forward operating location for US aircraft.

The five men originally arrested remain on police bail, while the latest suspect is being investigated on suspicion of preparation of terrorist acts.

No charges have been announced and the exact circumstances and intended purpose of the activity near RAF Fairford remain under investigation.