| United Kingdom of Great Britain and Northern Ireland | |
|---|---|
.svg) | |
| Nuclear program start date | 10 April 1940 |
| First nuclear weapon test | 3 October 1952 |
| First thermonuclear weapon test | 15 May 1957 |
| Last nuclear test | 26 November 1991 |
| Largest yield test | 3 Mt (13 PJ)(28 April 1958) |
| Total tests | 45 detonations |
| Peak stockpile | 520 warheads (1970s) |
| Current stockpile | 225[1][2][3] method of delivery (Trident IISLBM)[2] |
| Maximum missile range | 13,000 km (7,000 nmi or 8,100 mi) (UGM-133 Trident II) |
| NPT party | Yes (1968, one of five recognised powers) |
| Weapons of mass destruction |
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| Background |
| Nuclear-armed states |
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TheUnited Kingdom is one of the five officialnuclear-weapon states under theTreaty on the Non-Proliferation of Nuclear Weapons. It formerly possessedbiological, andchemical weapons.
As of 2025[update], the UKpossesses a stockpile of approximately 225 warheads, with 120 deployed on its only delivery system, theTrident programme'ssubmarine-launched ballistic missiles.[4][5] Additionally,United States nuclear weapons are stored atRAF Lakenheath since 2025, as well as between 1954 and 2008.[6][7]
The UK initiated the world's first nuclear weapons programme,Tube Alloys, in 1941 during theSecond World War. Under the 1943Quebec Agreement, it wasmerged with the USManhattan Project, butcollaboration ended in 1946. The UK initiated an independent programme,High Explosive Research,testing its first nuclear weapon in 1952. After theBritish hydrogen bomb programme's successfulOperation Grapple tests, the US resumed nuclear cooperation with the 1958Mutual Defence Agreement. This has involved the exchange ofclassified scientific data, warhead designs, andfissile materials. UK warheads are designed and manufactured by theAtomic Weapons Establishment.
In total the UK conducted 45 nuclear tests, 12in Australia, 9in the Pacific, and 24at the Nevada Test Site, with its last in 1991. The UK andFrance are the only two nuclear-armed countries that haveratified theComprehensive Nuclear-Test-Ban Treaty.
During theCold War, the UK developed a wide range ofnuclear weapons delivery systems, primarily itsstrategicV bomber fleet, and thetacticalWE.177 bomb. Witha US agreement, it operated thePolaris fleet ofballistic missile submarines from 1968, replaced by the Trident fleet beginning 1994. The US supplied warheads underProject E, as well as thePGM-17 Thor missile, and hosted US systems including theGround-Launched Cruise Missile,submarines at Holy Loch, andStrategic Air Command bombers.
The UK used chemical weapons extensively during theFirst World War, primarilychlorine,phosgene, andmustard gas, and inits intervention in the Russian Civil War employedadamsite. It possessed and researched chemical and biological weapons during and after the Second World War, centered atPorton Down. The causative agents ofanthrax,plague, andtularaemia, and others were tested. After the war, the UK experimented withnerve agents such assarin. In 1956, the UK renounced chemical and biological weapons, and later acceded to theBiological Weapons Convention andChemical Weapons Convention. It completed destruction of its chemical stockpile in 2007.[8]
During theSecond World War, British scientists studied the use of biological weapons, including a test usinganthrax on the Scottish island ofGruinard which left it contaminated and fenced off for nearly fifty years until an intensive four-year program to eradicate the spores was completed in 1990. They also manufactured five million linseed-oilcattle cakes with a hole bored into them for addition of anthrax spores between 1942 and mid-1943. These were to be dropped on Germany using specially designed containers each holding 400 cakes, in a project known asOperation Vegetarian. It was intended that the disease would destroy the German beef and dairy herds and possibly spread to the human population. Preparations were not complete until early 1944. Operation Vegetarian was only to be used in the event of a German anthrax attack on the United Kingdom.[9]
Offensive weapons development continued after the war into the 1950s with tests ofplague,brucellosis,tularemia and laterequine encephalomyelitis andvacciniaviruses (the latter as a relatively safe simulant forsmallpox).
In particular, five sets of trials took place at sea using aerosol clouds and animals.
The program was canceled in 1956 when the British government renounced the use of biological and chemical weapons. In 1974,biological weapons were banned, and the United Kingdom ratified theBiological and Toxin Weapons Convention in March 1975.
The UK was a signatory of theHague Conventions (1899 and 1907) which outlawed the use of poison gas in warfare. However, during theFirst World War, in retaliation to the use ofchlorine by Germany against British troops from April 1915 onwards, British forces deployed chlorine themselves for the first time during theBattle of Loos on 25 September 1915. By the end of the war, poison gas use had become widespread on both sides and by 1918 a quarter of artillery shells were filled with gas and Britain had produced around 25,400 tons of toxic chemicals.
Britain used a range of poison gases, originallychlorine and laterphosgene,diphosgene andmustard gas. They also used relatively small amounts of the irritant gaseschloromethyl chloroformate,chloropicrin,bromacetone andethyl iodoacetate. Gases were frequently mixed, for examplewhite star was the name given to a mixture of equal volumes of chlorine and phosgene, the chlorine helping to spread the denser but more toxic phosgene. Despite the technical developments, chemical weapons suffered from diminishing effectiveness as the war progressed because of the protective equipment and training which the use engendered on both sides. SeeUse of poison gas in World War I.
After the war, British forces reportedly usedadamsite againstBolshevik troops in 1919,[11]: 3 andWinston Churchill, secretary of state for war and air, suggested that the RAF use it inIraq in 1920 during a major revolt there. Historians are divided as to whether or not gas was in fact used.[12]
The UK ratified theGeneva Protocol on 9 April 1930. The UK signed theChemical Weapons Convention on 13 January 1993 and ratified it on 13 May 1996.
Despite the signing of theGeneva Protocol, the UK carried out extensive testing of chemical weapons from the early 1930s onwards. In theRawalpindi experiments, hundreds ofIndian soldiers were exposed tomustard gas in an attempt to determine the appropriate dosage to use on battlefields. Many of the subjects suffered severe burns from their exposure to the gas.[13]
Many ex-servicemen have complained about suffering long-term illnesses after taking part in tests on nerve agents. It was alleged that before volunteering they were not provided with adequate information about theexperiments and therisk, in breach of theNuremberg Code of 1947. Alleged abuses atPorton Down became the subject of a lengthy police investigation calledOperation Antler, which covered the use of volunteers in testing a variety of chemical weapons and countermeasures from 1939 until 1989. An inquest was opened on 5 May 2004 into the death on 6 May 1953 of a serviceman,Ronald Maddison, during an experiment usingsarin. His death had earlier been found by a privateMoD inquest to have been as a result of "misadventure" but this was quashed by theHigh Court in 2002. The 2004 hearing closed on 15 November, after a jury found that the cause of Maddison's death was "application of a nerve agent in a non-therapeutic experiment".
British nuclear weapons are designed and developed by the UK'sAtomic Weapons Establishment. The United Kingdom has fourVanguard-class submarines armed with nuclear armedTrident missiles. The principle of operation is based on maintaining deterrent effect by always having at least one submarine at sea, and was designed during theCold War period. One submarine is normally undergoing maintenance and the remaining two are in port or on training exercises.
Each submarine carries up to sixteenTrident II D-5 missiles, which can each carry up to twelve warheads, for a maximum of 192 warheads per vessel. However, the British government announced in 1998 that each submarine would carry only 48 warheads (halving the limit specified by the previous government), which is an average of three per missile. However one or two missiles per submarine are probably armed with fewer warheads for "sub-strategic" use causing others to be armed with more.
The British-designed warheads are thought to be selectable between 0.3kilotons, 5–10 kt and 100 kt; the yields obtained using either the unboosted primary, the boosted primary, or the entire "physics package". The United Kingdom has purchased the rights to 58 missiles under thePolaris Sales Agreement (modified for Trident) from theUnited States Navy's "pool". These missiles are fitted with United Kingdom–built warheads and are exchanged when requiring maintenance. Under the agreement the United States was given certain assurances by the UK regarding the use of the missiles; however the United States does not have any veto on the use of British nuclear weapons.[14][15] Some non-nuclear components for the British nuclear warhead are procured from the U.S. for reasons of cost effectiveness.[16]
The United Kingdom is one of the five "Nuclear Weapons States" (NWS) under theNuclear Non-Proliferation Treaty, which the UK ratified in 1968.
The UK permits the U.S. to deploy nuclear weapons from its territory, the first having arrived in 1954.[17] During the 1980s nuclear armed USAFGround Launched Cruise Missiles were deployed atRAF Greenham Common andRAF Molesworth. As of 2005 it is believed that about 110 tacticalB61 nuclear bombs are stored atRAF Lakenheath for deployment byUSAFF-15E aircraft.[18]
In March 2007, the UK Parliament voted torenew the country's Trident nuclear submarine system at a cost of £20 billion.[19] In July 2008,The Guardian claimed that the decision had already been made to replace and upgrade Britain's nuclear warhead stockpile at a cost of £3 billion, extending the life of the warheads until 2055.[20]
On 25 February 2020, the UK released a Written Statement outlining that the current UK nuclear warheads will be replaced and will match the US Trident SLBM and related systems.[21]
In March 2021, the British government published theIntegrated Review, titledGlobal Britain in a Competitive Age, which reaffirmed the government's commitment to upgrading and maintaining Trident as a continuous at-sea deterrent. The review also announced that the cap for the UK's stockpile of nuclear warheads would rise from 180 to 260 — the first time it has risen since the Cold War[22] — due to the "evolving security environment".[23]
In June 2025, the UK announced plans to purchase 12F35-A aircraft, that will carry both conventional and nuclear weapons, including theB61-12 gravity bomb. The aircraft will be based atRAF Marham in Norfolk as part ofNATO's dual capable aircraft programme.[24][25]
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