Updated: March 2017
The United Kingdom maintains an arsenal of 215 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. The UK is actively reducing its nuclear stockpile and plans to reach 180 nuclear weapons by the mid-2020s, which will represent a 65 percent reduction since the height of the Cold War. 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.
- The Nuclear Arsenal, an Overview
- Delivery Systems
- Ballistic Missile Defense Systems
- Fissile Material
- Proliferation Record
- Nuclear Doctrine
- Conference on Disarmament (CD)
- Nuclear Weapons Free Zones
- Nuclear Security Summits
- Joint Comprehensive Plan of Action (JCPOA)
Nuclear Nonproliferation Treaty
Convention on the Physical Protection of Nuclear Material (CPPNM)
CPPNM 2005 Amendment
International Convention for the Suppression of Acts of Nuclear Terrorism
Signatory, entered into force in 2004
The United Kingdom has filed the requested reports on its activities to fulfill the resolutions and volunteered to provide assistance to other states
The Nuclear Arsenal, an Overview
The United Kingdom (UK), as of 2017, maintains a military stockpile of 215 nuclear weapons and has reduced its deployed strategic warheads to 120, of which no more than 40 are at sea on the Vanguard-class submarines at any given time. The UK announced that it had achieved its commitment to reduce deployed warheads to 120 in January 2015.
The UK has the smallest deployed arsenal of the nuclear weapons states and has committed to reducing its nuclear stockpile. In October 2010, the UK government announced plans to reduce its total nuclear weapons stockpile to 180 weapons by the mid-2020s. It reaffirmed this commitment in its 2015 Strategic Defence and Security Review (SDSR).
Upon successful reduction down to 180 nuclear warheads, the UK will have achieved a 65 percent reduction in the size of its overall nuclear stockpiles since the height of the Cold War. Plans to modernize the UK’s nuclear arsenal were introduced in 2006 but have, presently (March 2017), been deferred. The cornerstone of modernization plans surrounds the introduction of a new nuclear-capable submarine to replace the Vanguard-class.
Intercontinental Ballistic Missiles (ICBM)
- The United Kingdom’s does not possess ICBMs.
Submarines and Submarine-Launched Ballistic Missile (SLBM)
- British nuclear warheads are only deployed on 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 D-5 missiles are equipped with British warheads similar to the United States’ W76 100 kt warheads.
- The Trident D5 is planned to remain in service until the early 2040s following a life extension program. Decisions for a replacement warhead have been deferred until later this decade and the current warhead is expected to last into the late 2030s.
- The British military currently operates four Vanguard-class nuclear-powered ballistic missile submarines (SSBNs). Each submarine is capable of carrying 16 Trident D5 missiles and each of these missiles carry up to three 100 kt warheads. Currently each submarine only carries up to eight Trident D5s.
- One submarine is always out at sea on deterrent patrol. The missiles aboard the Vanguard, however, are not 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.
- At the cornerstone of the UK’s nuclear weapons modernization ambitions, the British government declared it intentions in 2015 to replace the Vanguard-class submarines in what is known as the Successor submarine program. This program entered its design phase as early as 2011. It is estimated that the production of four Successor submarines will cost £31 billion. In keeping with an anti-Trident campaign, there exists debate over whether or not to carry out this program.
- 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 Successor 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 Vanguard-class is expected to leave service by the early 2030s.
- Although the UK’s nuclear modernization plans enjoy strong support from the government, particularly from the Conservative Party, there are those in the government, mainly in the Labour Party—with current Opposition Leader Jermey Corbyn at the forefront, who oppose these plans amid rising public skepticism about the need to possess nuclear weapons. 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 was 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 submarines if Scotland obtained independence.
- 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."
- In April 1995, the UK ceased production of separated plutonium and the British government declared that it no longer produces fissile material for weapons. The UK halted the production of highly enriched uranium (HEU) in 1963. As of 2016, the British government is estimated to maintain a military stockpile of approximately 3.2 metric tons of plutonium and 19.8 metric tons of HEU.
- The United Kingdom possesses the world’s largest stockpile of civilian plutonium, with over 103.3 metric tons designated for this purpose.
- In 2014, the UK announced that it will shut down its B205 plutonium reprocessing plant around 2020. The plant reprocessed spent fuel from the UK’s Magnox power reactors.
- The country stores approximately 23 metric tons of foreign owned plutonium, the majority of which belongs to Japan.
- The UK’s civilian stockpile of HEU is roughly 1.4 metric tons.
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.
In its 2015 Strategic Defense and Security Review document, the British government reaffirmed a commitment not to use nuclear weapons against non-nuclear-weapon states-parties to the Nuclear Nonproliferation Treaty (NPT) subject to certain conditions regarding their behavior and alliances. Nevertheless, this 2015 document notes that the government reserves the right to “review this assurance if the future threat, development or proliferation of these weapons make it necessary.” The document also states that “We will continue to keep our nuclear posture under constant review in the light of the international security environment and the actions of potential adversaries.” London refuses to rule out the first use of nuclear weapons, but has stated that it would only employ such arms in self-defense and “even then only in extreme circumstances.”
The UK’s 2006 defense white paper states that “we deliberately maintain ambiguity about precisely when, how and at what scale we would contemplate use of our nuclear deterrent.”
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.
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 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 (BTWC) in March 1975 and has reaffirmed its support for the BTWC in 2005.
- Today, the British government operates an extensive and sophisticated defensive program that includes research on potentially offensive pathogens.
- 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.
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.
Nuclear Weapons Free Zones
The United Kingdom has ratified additional protocols to the Latin American and the Caribbean, South Pacific, African, and Central Asian nuclear weapons free zone treaties pledging not to use or threaten to use nuclear weapons against the treaty's member states. However, the UK maintains reservations to each of these protocols. It has not ratified the Southeast Asia nuclear weapons free zone treaty.
Nuclear Security Summits
British participation in the Nuclear Security Summits includes the 2010 Nuclear Security Summit (NSS) in Washington, DC, the 2012 NSS in Seoul, the 2014 NSS in The Hague, and the 2016 NSS held again in Washington, DC.
Joint Comprehensive Plan of Action (JCPOA)
London has engaged in nonproliferation negotiations with Iran such as the most recent rounds of the P5+1 talks over Iran’s nuclear activities. The British government supported ratcheting up sanctions on Iran to persuade it to halt certain activities, particularly uranium enrichment. This included a European Union-wide ban on importing Iranian oil that went into effect July 1, 2012. The UK participated in negotiations on the JCPOA in July 2015 which both limits and rolls back Iran’s nuclear program. Then Prime Minister David Cameron said that the deal would "make our world a safer place."