Recent developments have underscored the increased security concerns for U.S. military facilities in the United Kingdom stemming from the ongoing conflict involving Iran. A former British counterterrorism leader emphasized this risk, following the arrest of five individuals suspected of plotting a terrorist attack near RAF Fairford, a U.S.-operated base.

The arrests occurred in Gloucestershire, near Whelford, where RAF Fairford has historically been a site utilized by American bombers, including those deployed during the Iran conflict initiated by former President Donald Trump on February 28. Although investigators have yet to determine whether the plot was state-backed, Iran has previously targeted U.S. military sites in the Middle East, and there have been hints that U.S. bases in Europe might also be potential targets.

Chris Phillips, former head of the U.K’s National Counter Terrorism Security Office, expressed concerns about the enduring risk to U.S. facilities in the U.K., stating to Newsweek that the threat remains significant. “The threat is real,” Phillips noted, adding, “It’s not going to go away even when the war finishes.” He further commented on the possibility of an existing bomb factory and the creation of explosives.

A spokesperson from the U.S. Department of Defense mentioned that U.S. European Command remains vigilant and committed to ensuring the safety of U.S. service members, civilians, contractors, and their families throughout Europe.

On Monday, Gloucestershire police interrogated the five unnamed suspects, initially arrested for suspected explosives offenses, later on suspicion of preparing a terrorist act. British intelligence has previously identified Iran and Russia as using proxies for activities within the U.K., noting a significant rise in hostile state activities up to December 2025.

Phillips expressed skepticism over President Donald Trump’s remark regarding cooperation between U.S. and U.K. forces that allegedly led to the suspects’ arrest, doubting the extent of surveillance on the suspects. He emphasized the improbability that British police would allow an active threat to proceed without intervention.

“I think it’s unlikely they were under tight surveillance,” Phillips said, highlighting the heightened awareness of potential threats at RAF Fairford.

Security measures appeared to increase before the arrests, prompted by reports from a local farmer who noticed suspicious activity near the base. Her alert led to heightened response, including evacuations of around 85 homes as detectives continued their investigations.

Phillips criticized the suspect group, suggesting their approach was amateurish and not that of “high-quality terrorists” despite their intentions to use explosives.

U.S. Bases in the U.K.

RAF Fairford serves as the headquarters for the U.S. 501st Combat Support Wing and the 420th Air Base Squadron. Although the U.K. did not join the U.S.-Israeli offensive against Iran, it later permitted U.S. operations for “defensive” purposes.

Additional U.S. presence includes RAF Lakenheath and Mildenhall, supporting various air operations and refueling tasks. The U.S. Department of Defense has raised threat levels at these bases, reflecting the increased security measures following recent events.