Nuclear Information: British nuclear weapon stockpile

The British nuclear stockpile is estimated to be approximately 160 Trident submarine-launched ballistic missile (SLBM) warheads.

The British Prime Minister is the ultimate authority over the use of British nuclear weapons. British nuclear weapons are researched, produced, and controlled by the Ministry of Defence (MOD), under the overall supervision of the Chief of the Defence Staff and the Permanent Secretary. Nuclear weapons are currently deployed only with the Royal Navy (RN). The Atomic Weapons Establishment (AWE), an organization of the MOD, is the British equivalent of the Department of Energy's defense programs. Nuclear warheads are designed by the AWE at Aldermaston and assembled and disassembled at Aldermaston and Burghfield.

The Royal Navy (RN) currently possesses four operational ballistic missile submarines. Britain originally built and deployed four Resolution-class SSBNs, commonly called Polaris submarines for the missiles they carried. The first boat (HMS Resolution) went on patrol in mid-June 1968, the fourth (HMS Revenge) in September 1970. Today construction, training, testing, and sea trials continues with the $18.8 billion Vanguard-class ballistic missile submarine (SSBN) program. Designed and built by Vickers Shipbuilding and Engineering, each Vanguard-class boat displaces some 16,000 tonnes, about twice as much as the Polaris/Resolution-class SSBNs they replace. Each carries sixteen U.S. produced Trident II D-5 Submarine Launched Ballistic Missiles (SLBM).

The first submarine of the class, the HMS Vanguard, went on its first patrol in December 1994.The second, HMS Victorious entered service in December 1995. The third, HMS Vigilant was launched in October 1995. The fourth and final boat of the class, HMS Vengeance is now also in service.

Not only do the Vanguard boats use the U.S. Trident II missile, but the American and British missiles are thought to be interchangeable. There is a pool of SLBMs at the Strategic Weapons Facility Atlantic at the Kings Bay Submarine Base, Georgia. Britain has title to an eventual 70 missiles but it does not actually own them outright. Thus a missile that is deployed on a U.S. SSBN may at a later date deploy on a British one, or vice versa. When a Vanguard-class SSBN is ready to enter service it sails to Kings Bay, collects missiles and conducts one or two demonstration/shakedown test firings at the eastern missile range off Cape Canaveral, Florida. When ready to deploy it is loaded with a full complement of missiles, sailing back to the Royal Naval Armament Depot at Coulport where the nuclear warheads are mated.

British Trident II missiles carry a British-designed nuclear warhead, 160 of which are estimated to be in the stockpile today. As few as 40 and as many as 115 remain to be produced, depending on future plans. The first batch was completed in September 1992. The warheads are thought to be similar in size, shape, and yield to the U.S. W76 warhead. The estimate of 275 total warheads for the British Trident II program assumes that only enough warheads will be produced for three boatloads of missiles, a practice followed with Polaris as well (240 warheads for 48 missiles, assuming five warheads per missile, plus another ten percent for spares and maintenance).

As Britain settles on its single leg nuclear force, it is also implementing a program to assign a "sub-strategic" (tactical) mission to the Trident missile and submarine. This means that the number of nuclear warheads on operational missiles will likely be even lower for those vessels and missiles placed in the sub-strategic pool. A MOD official described the program as follows: "A sub-strategic strike would be the limited and highly selective use of nuclear weapons in a manner that fell demonstrably short of a strategic strike, but with a sufficient level of violence to convince an aggressor who had already miscalculated our resolve and attacked us that he should halt his aggression and withdraw or face the prospect of a devastating strategic strike."

The sub-strategic mission has begun with HMS Victorious and, according to the 1996 White Paper, "will become fully robust when Vigilant enters service." The plan is to put a single warhead on some Trident II SLBMs and have them assigned to NATO-assigned targets once covered by WE177 gravity bombs (and presumably other targets for U.K. contingencies). For example, a submarine could be armed with 10, 12 or 14 of its SLBMs carrying an average of five warheads per missile, and the other two, four or six missiles armed with just one. There is some flexibility in the choice of yield of the British Trident warhead as well. (Choosing to only detonate the unboosted primary could produce a yield of one kiloton or less. Choosing to detonate the boosted primary could produce a yield of a few kilotons.)

An elite component of the Royal Marines is responsible for guarding British nuclear weapons and ballistic missile submarines. Known as the Commachio Group, the unit was first formally activated in May 1980. The key naval installation they guard is the Royal Naval Armament Depot (RNAD) Coulport in Scotland, where British ballistic missile submarine (SSBN) missiles and warheads are stored. Commachio commandos escort the submarine out to open waters, ostensibly to protect it from terrorist attacks and anti-nuclear demonstrators.

The unit is named after Lake Commachio, north of Ravenna, Italy, where Royal Marine Tom Hunter won the Victoria Cross in World War II. Commachios were selected from Royal Marine commando units and the number eventually grew to number 350. Other missions that they have responsibility for include anti-smuggling operations and protection of U.K. oil rigs in the North Sea.