The United Kingdom is a nuclear-armed state, estimated by the SIPRI Yearbook 2011, and in accordance with the Coalition Government’s 2010 Strategic Defence and Security Review (SDSR), to possess no more than 225 nuclear weapons, of which some 160 are operationally available.  After British scientists participated in the US Manhattan Project, the UK clandestinely pursued a nuclear weapons programme of its own before going public with its first nuclear test on 3 October 1952 at Montebello, Australia.  The UK conducted 45 nuclear tests at various Pacific sites and then the US Nevada Test Site before the 1992 US moratorium forced Britain’s nuclear testing programme to an end.

Though it developed a range of different nuclear forces during the Cold War, the UK now deploys only one system, using UK warheads on US Trident missiles carried on four Vanguard-class nuclear submarines.  After an in-principle decision by Parliament in 2007 to procure 4 new submarines and renew the Trident-based nuclear weapons to 2050 at an estimated cost of £76-100 billion, public opposition to the replacement of Trident has been increasing.  The ‘main gate’ procurement decision has been delayed until 2016, amid growing questions about the purpose and affordability of replacing Trident.  Debates in Scotland over independence are also calling the feasibility of Trident replacement into question, as the UK’s nuclear warheads are stored in Scotland at Coulport, close to the Faslane naval base where the submarines are home-ported.   UK nuclear warheads are designed and manufactured at the Atomic Weapons Establishments (AWE) at Aldermaston and Burghfield, near London.

The UK is a depositary state for the Nuclear Nonproliferation Treaty and one of the treaty’s five defined Nuclear Weapon States (NWS).  The UK signed and ratified the Comprehensive Test Ban Treaty (CTBT) in 1998.  The UK is a state party to the Biological and Toxin Weapons Convention (BWC) and a state party to the Chemical Weapons Convention (CWC).  As at January 2012, the UK is a state party to the Mine Ban Treaty and a state party to the Convention on Cluster Munitions (CCM). It is a member of NATO (North Atlantic Treaty Organization). It is a member of the 65-nation Conference on Disarmament (CD).   It is a member of the Nuclear Suppliers Group (NSG).