Counter-terror police have arrested a 25-year-old UK-Iranian dual national in Westminster, London, on suspicion of preparation of terrorist acts in connection with a recent incident at RAF Fairford in Gloucestershire. Two properties in London have been searched as part of the ongoing investigation.

The incident at the airbase, which is operated by the US Air Force, began on Sunday when three suspicious vehicles were reported travelling towards the site. This led to a major security alert and the arrest of five men, all UK nationals from London, who were initially detained on suspicion of explosives offences.

Authorities later updated the age of the dual national to 25 and clarified that a second man had not been questioned under caution. The five men arrested near the airbase, aged between 23 and 25, were later released on police bail. Police stated that a quantity of petrol was found near the site, but no explosive devices were recovered.

Prime Minister Andy Burnham indicated on Wednesday that there were strong indications of Iran's involvement in the events, although he did not provide specific details. Iran has strongly denied any participation. The US Secretary of State, Marco Rubio, also suggested on Monday that a foreign actor was clearly involved in the incident.

RAF Fairford has been used as a forward operating location by the USAF for decades. In recent months, US bombers have departed from the base for missions in the Middle East, following the UK's approval of a US request for the base to be used for defensive strikes against Iran.

Counter-terror police are examining all potential angles, including the possibility of foreign state involvement. Vicki Evans, the force's senior national coordinator, described the investigation as "hugely complex" and confirmed that multiple lines of inquiry are being pursued by specialist teams.

The five men released on bail were from Westminster and Camden, and searches of their homes were conducted. Police described their decision to release the men on bail as an "investigative decision that was grounded in experience and strategy."

The investigation continues as authorities work to understand the full circumstances surrounding the incident and the potential motivations behind it.