Which UK bases can US use to strike Iranian missile sites, why are they so critical?

The United Kingdom has authorised the United States to use its military bases for strikes on Iranian missile sites targeting shipping in the Strait of Hormuz. On Friday, Downing Street announced that the agreement the falls under “collective self-defence of the region,” permitting “defensive operations to degrade the missile sites and capabilities being used to attack ships.” The move marks a shift by Prime Minister Keir Starmer, who had initially resisted involvement while seeking legal clarity.

The US has been granted access to two key facilities: RAF Fairford and Diego Garcia. These are the only UK bases confirmed for such operations. While one sits in southwest England, the other lies deep in the Indian Ocean, giving the US both regional reach and global strike flexibility.

RAF Fairford, located in Gloucestershire, England, is operated by the United States Air Force and serves as a key forward operating location in Europe. It supports heavy bombers such as the B-52, B-1B and B-2, aided by one of the longest runways in the UK. The base hosts the 501st Combat Support Wing Headquarters and forms part of the 422d Air Base Group. Its infrastructure enables long-range missions and regular Bomber Task Force deployments. Since early March, US bombers have operated from Fairford on “defensive missions to destroy Iran’s missile capabilities,” underlining its strategic role.

Diego Garcia, around 4,000 km from Iran, is a joint UK–US base central to American operations in the Indian Ocean. Despite its remote size, it supports long-range bomber missions, naval replenishment, and prepositioned military supplies.The air base is home to about 2,500 mostly American personnel and has supported US military operations from Vietnam to Iraq, Afghanistan and strikes on Yemen’s Houthi rebels.

Iran had warned that any use of UK bases constitutes “participation in aggression.” Tehran's Foreign Minister Abbas Araqchi stated Britain was “putting British lives in danger.” On Saturday, Iran attempted a missile strike on this base, marking one of its longest-range actions yet. The United Kingdom condemned the move as “reckless,” with the Ministry of Defence stating Iran’s actions “threaten British interests and allies” and destabilise the Strait of Hormuz. The strike attempt followed London’s decision to allow the United States to use UK bases against Iran.

These bases provide secure, politically reliable launch points outside the volatile Gulf region. They reduce dependence on Middle Eastern host nations while enabling sustained air operations, logistics, and rapid deployment. Diego Garcia’s isolation enhances survivability, while Fairford offers immediate access to strategic bomber fleets.

British officials stress the authorisation is for “specific and limited defensive operations.” However, the decision underscores the UK’s strategic importance to US military planning and its delicate position between alliance commitments.