Police have now detained seven people, and released six on bail, in connection with the incident near an air base used by U.S. warplanes that President Trump and Britain's leader say has Iran links.
British police on Tuesday arrested a 22-year-old man in London on suspicion of a terror offense over a security incident at a U.S.-run military air base in England that authorities have linked to Iran. It was the seventh arrest in connection with a suspected plot against RAF Fairford, 100 miles west of London, which has been used by American bombers to strike Iran during the ongoing war.
The U.K.'s Counter Terrorism Policing force said the man, a British national, was detained in the Westminster area of central London on suspicion of preparation of terrorist acts.
The six other men who were arrested as part of the investigation have been released on bail, under investigation and monitoring. The decision to bail them drew criticism last week from President Trump.
Vicki Evans, the senior national coordinator for counterterrorism policing, said detectives "continue to pursue multiple lines of enquiry" and "remain committed to investigating all possible angles."
Scores of residents were evacuated from their homes near the base early on Sept. 27 as armed police officers and army bomb-disposal experts swooped on the rural area. Police later said they had found a quantity of an accelerant — gasoline — in three vans linked to the five suspects, but no explosives.
Prime Minister Andy Burnham has said the U.K. sees "strong indications" that Iran played a part in the incident, without saying why or what the nature of the suspected plot was.
Mr. Trump had previously said Iran "might be" involved, telling reporters on Sept. 28 that U.S. and British authorities worked "very closely" on the matter and "we know everything about them. We would not have released them" from custody.
Iran has denied involvement, but it has previously said it considers any base used to attack its territory a legitimate target.
The U.S. moved its B-52 and B-1 bombers from RAF Fairford on Sunday, though it's unclear whether or how the move was connected to the arrests. Mr. Trump told reporters on Monday he didn't want to tempt "the enemy" by having the bombers there.
"We had a threat, and if we're going to be threatened, we would just move them, and that sort of alleviates that," he said in Washington, adding that the people behind the unspecified threat "would be linked to Iran," without offering details.