The Vanguard-class submarines that carry the nuclear warheads and missiles are coming to the end of the life. Their replacement is known as the Successor.
In light of the lengthy procurement process required for complex weapons systems, Parliament voted in 2007 to “maintain the strategic nuclear deterrent beyond the life of the existing system.” The Government had, the year before, published a White Paper outlining its intention to build a new class of submarines, with a final decision on whether three or four boats are needed to maintain CASD to be taken when more is known about the design.
The Government decided in the Strategic Defence and Security Review of 2010 to delay Main Gate until 2016. This is when the main investment decision on a programme is taken. Initial gate was passed in 2011, releasing funds for a five year assessment phase. Previously, the 2006 White Paper suggested Main Gate would fall between 2012 and 2014. The Government will decide at Main Gate how many boats to procure.
Both the Conservative Party and the Labour Party have committed to maintaining Continuous-at-sea Deterrent. The Liberal Democratic Party favours ending the Continuous-at-sea posture and reducing it to a Contingency Posture with fewer boats. Upon entering the Coalition, the Liberal Democratic Party secured the agreement of the Conservative Party to study the costs, feasibility and credibility of alternative systems and postures for the nuclear deterrent. This became known as the Trident Alternatives Review. It was published in July 2013. The review does not make recommendations and is not a statement of Government policy.
The Ministry of Defence has committed to providing annual reports to Parliament on the status of Successor programme. The most recent was published in December 2014.
The Ministry of Defence estimates the cost of the Successor programme to fall within the 2006 White Paper estimates of £15-20bn, including 11-14 billion for the new submarine (at 2006-7 prices). The in-service costs of the UK’s nuclear deterrent amount to approximately 5-6% of the defence budget. Opponents of the nuclear deterrent, such as CND, suggest the lifetime costs of the deterrent will amount to £100 billion.
Trident is based in Scotland and was a major issue in the build-up to the referendum for independence in September 2014 because of the Scottish Government’s commitment to secure “the speediest safe withdrawal of nuclear weapons from Scotland” within the first term of the Scottish Parliament following independence, if that had been the outcome of the referendum.
Successive Governments have insisted that replacing Trident is compatible with the UK’s obligations under the Nuclear Non-Proliferation Treaty (NPT), arguing that the treaty contains no prohibition on updating existing weapons systems and gives no explicit timeframe for nuclear disarmament.