Arms Control and Proliferation Profile: The United Kingdom

The United Kingdom maintains an arsenal of 225 nuclear weapons and has reduced its deployed strategic warheads to 120, which are fielded solely by its Vanguard-class submarines under its maritime-only deterrence strategy. After significantly reducing its nuclear stockpile since the height of the Cold War, the UK now plans to retain a maximum of 260 warheads. The British government’s standard practice is to have one submarine on deterrent patrol at any given time, though it claims the missiles are not on alert and would take several days of preparation before launching.

Contents

Major Multilateral Arms Control Agreements and Treaties

Export Control Regimes, Nonproliferation Initiatives, and Safeguards

Nuclear-Weapon-Free Zone Negative Security Assurances

Nuclear Weapons Programs, Policies, and Practices

• The Nuclear Arsenal, an Overview
• Delivery Systems
• Ballistic Missile Defense Systems
• Fissile Material
• Proliferation Record
• Nuclear Doctrine

Biological Weapons

Chemical Weapons

Other Arms Control and Nonproliferation Activities

• Conference on Disarmament (CD)

Major Multilateral Arms Control Agreements and Treaties

Export Control Regimes, Nonproliferation Initiatives, and Safeguards

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Nuclear-Weapon-Free Zone Negative Security Assurances

For an introduction to the Nuclear-Weapon-Free Zones, see our factsheet.

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Nuclear Weapons Programs, Policies, and Practices

The Nuclear Arsenal, an Overview

Delivery Systems

Intercontinental Ballistic Missiles (ICBM)

• The United Kingdom does not possess ICBMs.

Submarines and Submarine-Launched Ballistic Missile (SLBM)

Submarines:

• The British military currently operates four Vanguard-class nuclear-powered ballistic missile submarines (SSBNs). Each submarine is capable of carrying 16 Trident D5 missiles. As of 2019, each submarine carried a maximum of eight Trident II D5 submarine-launched ballistic missiles (SLBMs). In 2021, the UK announced it would no longer disclose the number of deployed missiles on SSBNs. 
• One submarine is always out at sea on deterrent patrol. The missiles aboard the Vanguard, however, are not on alert and require several days of preparation prior to launching.
• The Vanguard SSBNs are housed at Her Majesty's Naval Base (HMNB) Clyde off the shore of Gare Loch in Scotland.
• The UK government will replace the Vanguard-class submarines with what was formerly known as the Successor submarine program. This new submarine was named the Dreadnought-class in October 2016, and is expected to have a lifespan of at least 30 years. According to a November 2018 report by BASIC Institute, the UK government has estimated that the Dreadnought program will cost £31 billion with an additional £10 billion contingency. Over the 30-year lifetime of a new system that emerges into service in 2031, the total in-service costs could range between £71.4 billion and £140.5 billion. 
• In June 2012, the British government awarded a contract to Rolls-Royce to build two new nuclear submarine reactor cores. The second of these cores is for the first Successor class vessel.
• In October 2016, construction of the first new submarine began under BAE Systems and has been named the HMS Dreadnought. The Dreadnought will be the Royal Navy’s largest-ever submarine at 17,200 metric tons, 1,300 metric tonnes heavier than the Vanguard. It will be only be fitted with 12 missile tubes for the Trident D5 instead of 16.
• The British Royal Navy has announced that the Dreadnought-class ballistic missile submarines will be named: HMS King George VI, HMS Dreadnought, HMS Valiant, and HMS Warspite.
• There exists debate over whether or not to carry out this program. Opposition to modernization plans are chiefly due to its high cost (it is slated to be the largest British military project in history), time commitment, prevailing pro-disarmament sentiments, and safety concerns.
• Scottish, Welsh, and Irish nationalist parties are also generally pro-disarmament. In addition, the future of the UK’s nuclear weapons could have been jeopardized by the Scottish independence referendum in 2014 as its nuclear submarines are housed at HMNB Clyde in Scotland and the Scottish Nationalist Party vowed to scrap the Vanguard-class submarines if Scotland obtained independence.

• British nuclear warheads are only deployed on submarine-launched ballistic missiles (SLBMs).
• The United Kingdom maintains one type of ballistic missile system in its arsenal for delivering nuclear warheads: the U.S.-leased Trident II (D5) SLBM, which has an estimated range of roughly 7,400-12,000 kilometers. The UK’s Trident D5 missiles are equipped with British warheads similar to the United States’ W76 100-kiloton warheads.
• The UK plans to retain the Trident D5 in service until the 2080s following two life extension programs. 
• In 2020, the UK announced it would replace its current warheads with a new design similar to the in-development U.S. W93 warhead. It will be housed in the Mk7 aeroshell that is in parallel development by the U.S. Navy.

Strategic Bombers

• The United Kingdom does not possess nuclear capable aircraft.
• Britain’s dismantlement of the Royal Air Force’s gravity based nuclear bombs in 1998 marked the beginning of its maritime-only deterrence strategy.

Ballistic Missile Defense Systems

The United Kingdom is part of the European Phased Adaptive Approach (EPAA), a collective missile defense system operated by NATO allies. To learn more, see: "The European Phased Adaptive Approach at a Glance."

Fissile Material

• In April 1995, the UK ceased production of separated plutonium and the British government declared that it no longer produces fissile material for weapons.

Highly Enriched Uranium (HEU)

• The UK halted the production of highly enriched uranium (HEU) in 1963. As of April 2024, the British government is estimated to maintain a military stockpile of approximately 21.9 metric tons of HEU.
• The UK's civilan stockpile of HEU is roughly 1.4 metric tons.

Plutonium

• The UK maintains a military stockpile of an estimated 3.2 metric tons of plutonium.
• The United Kingdom possesses the world’s largest stockpile of civilian plutonium, with over 116.4 metric tons designated for this purpose, as of December 2022.
• The UK operated two reprocessing plants. The B205 plutonium reprocessing plant, which reprocessed fuel from the Magnox reactors in Sellafield, England, was shut down in 2022. The Thermal Oxide Reprocessing plant (THORP), which reprocessed mixed oxide fuel, closed in November 2018. 
• According to the Houses of Parliament 2016 report, “Managing the UK Plutonium Stockpile,” the country stores approximately 23 metric tons of foreign-owned plutonium, the majority of which belongs to Japan.

Proliferation Record

• The UK is not known to have deliberately or significantly contributed to the spread of biological, chemical, or nuclear weapons to other states.
• The UK is, officially, an active promoter of nonproliferation and is a leading member in the Nuclear Suppliers Group, the Australia Group, the Missile Technology Control Regime, and the Zangger Committee as well as the Proliferation Security Initiative.
• The UK has been involved in both Iranian and Libyan nonproliferation processes and continues to support the creation of an effective and verifiable chemical, biological, radiological, and nuclear-free zone in the Middle East.   

Nuclear Doctrine

In its 2021 Integrated Review of Security, Defence, Development and Foreign Policy, the UK government reaffirmed a commitment not to "use, or threaten to use, nuclear weapons against any non-nuclear weapon state party to the Treaty on the Non-Proliferation of Nuclear Weapons." This policy excludes states which are in material breach of their nonproliferation commitments. The review also stated that the UK might reconsider the commitment in the face of the "future threat of weapons of mass destruction, such as chemical and biological capabilities, or emerging technologies that could have a comparable impact."

The United Kingdom does not maintain a no-first-use policy, but says it will use "nuclear weapons only in extreme circumstances of self-defence, including the defence of our NATO Allies."

The British government’s standard practice is to have one submarine on deterrent patrol at any given time. The government claims the missiles aboard the submarine are not on alert and that launching a missile would take several days of preparation.

Testing

The United Kingdom has conducted 45 nuclear weapon tests. The first test occurred on October 3, 1952, and the last took place November 26, 1991. The United Kingdom was the third country to conduct a nuclear test. 

For a full record of the United Kingdom's nuclear testing, see our Nuclear Testing Tally factsheet. 

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Biological Weapons

• The United Kingdom had an active biological warfare program from 1934 to 1956.
• As part of that program, the United Kingdom weaponized anthrax and researched plague, typhoid fever, and botulinum toxin.
• The United Kingdom ratified the Biological and Toxin Weapons Convention (BWC) in March 1975 and has reaffirmed its support for the BWC in 2005.
• Today, the British government operates an extensive and sophisticated defensive program that includes research on potentially offensive pathogens.

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Chemical Weapons

• During World War I, the United Kingdom produced an arsenal of chlorine and mustard gases.
• In 1957 the UK abandoned its chemical weapons program and has since eradicated its stockpiles.
• The UK ratified the Chemical Weapons Convention (CWC) in 1996 and has provided financial assistance to countries such as Russia, in 2001, to destroy their chemical weapons stockpiles.

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Other Arms Control and Nonproliferation Activities

Conference on Disarmament (CD)
The United Kingdom regularly participates in the CD, established in 1979 by the international community as a multilateral disarmament negotiating forum. In July 2009, the British government announced its report on nuclear nonproliferation entitled “The Road to 2010” at the CD. In 2010, the UK called for negotiations on an Fissile Material Cutoff Treaty (FMCT) to be moved to the United Nations General Assembly where it could be endorsed by a majority vote.  

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