Fact Check: UK Manufactures Warheads for Trident Missiles

In a statement that has sparked debate about the UK’s nuclear capabilities, Green Party leader Zack Polanski claimed that Britain’s nuclear warheads are leased from the United States, raising questions about the independence of the country’s nuclear deterrent program.

“Trident… doesn’t work & leases the warheads from… the USA,” Polanski stated in a recent social media post, referring to the submarine-launched ballistic missile system that forms the backbone of the UK’s nuclear arsenal.

However, official information from the Ministry of Defence (MoD) contradicts this assertion. According to the MoD, while the Trident missile system itself is designed and manufactured in the United States, the nuclear warheads—the explosive devices fitted to these missiles—are produced domestically in the United Kingdom.

“Warhead design and manufacture is carried out at AWE Nuclear Security Technologies in Berkshire,” the MoD clarifies on its official website. This facility, formerly known as the Atomic Weapons Establishment, is responsible for maintaining Britain’s nuclear warhead capability.

The relationship between the UK and US regarding nuclear weapons is complex but clearly defined. The procurement arrangement for the Trident system operates under the 1963 Polaris Sales Agreement (PSA), which was later amended to accommodate the Trident system. Under this agreement, the UK purchases a specific number of missiles from a shared stock maintained at Kings Bay Submarine Base in Georgia, USA.

Britain’s nuclear-armed submarine fleet, currently consisting of the Vanguard Class vessels, collects these missiles from the US and transports them to Scotland. It is only at His Majesty’s Naval Base Clyde where the UK-manufactured warheads are fitted to the American-made missiles.

Defense experts note that this arrangement represents a partnership rather than a lease. Dr. Matthew Harries of the Royal United Services Institute explained in a previous analysis, “The UK has full operational independence over its nuclear deterrent, though it does rely on American technical support for the missile system.”

The UK’s nuclear deterrent consists of four Vanguard Class submarines, with at least one always on patrol, carrying up to 16 Trident II D5 missiles. Each missile can be armed with multiple warheads, though the exact number is classified for security reasons.

This cooperative arrangement with the United States is set to continue when the next generation of British nuclear submarines—the Dreadnought Class—enters service in the coming years. These new submarines represent a significant investment in Britain’s nuclear capabilities, with the program estimated to cost more than £30 billion over its lifetime.

While the UK maintains operational independence over its nuclear arsenal, it does rely on American technical expertise for maintenance of the missile system. This interdependence has led some defense analysts to question whether Britain could operate its nuclear deterrent without US support in a crisis—a point that critics like Polanski appear to be highlighting, albeit inaccurately.

The Atomic Weapons Establishment employs approximately 6,000 staff and plays a critical role in Britain’s defense infrastructure. The facility not only manufactures and maintains the current warhead stockpile but also conducts research into future nuclear weapons technology.

Britain’s nuclear deterrent policy has remained largely consistent across governments since the Cold War, with both Conservative and Labour administrations supporting the maintenance of a continuous at-sea deterrent force. The Green Party, led by Polanski, has consistently opposed nuclear weapons on both security and moral grounds.

As global tensions rise and several nations upgrade their nuclear arsenals, the accuracy of public statements about Britain’s nuclear capabilities takes on added importance in informing democratic debate about defense policy and strategic autonomy.