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Scotland referendum 2014: the impact of independence on Trident

Analysis of the potential impact of a Yes vote in the Scottish independence referendum on Trident.

Part of a collection of articles produced by the House of Commons Library which explore the potential impact of a Yes vote on the UK, aiming to inform the debate from an impartial viewpoint.


The UK nuclear deterrent is based in Scotland

The Scottish Government wants it removed quickly in the event of independence

It is hard to see where it could go instead and moving it would be expensive

The Scottish Government has prioritised the removal of Trident nuclear submarines from Scotland in the event of independence. The implications for the UK's strategic nuclear deterrent are considerable. Where the submarines and the associated warhead depot might go, who will pay the relocation costs and how long it might take will be subject to negotiation – complicated by the fact there is no obvious alternative base.

What is Trident?

Trident is the UK's strategic nuclear deterrent system. It is composed of three parts: the warhead, the delivery system (ballistic missiles) and the platform (submarine).

The nuclear warheads are mounted on Trident II D5 missiles which are launched from Vanguard-class nuclear powered submarines. There are four submarines and they maintain a Continuous-at-sea deterrence (CASD), meaning one is always out on patrol, on Operation Relentless.

Nuclear warheads can be carried on a number of delivery vehicles and platforms. The UK is the only recognised nuclear weapon state to have reduced its nuclear capability to a single platform. France has two delivery systems – submarines and air-launched missiles, while the United States, China and Russia operate a triad of delivery systems – air, land and sea.

The Scottish Government, in the White Paper Scotland's Future, has prioritised “early agreement on the speediest safe removal of nuclear weapons” from Scotland, with a view to the removal happening within the first term of the Scottish Parliament following independence.

The simple solution for the UK Government, in the event of independence, is to move the submarines and stored warheads elsewhere in the UK. However there is no obvious alternative location and the UK Government, in its Scotland analysis: Defence paper, suggests relocating the nuclear deterrent “would cost billions of pounds and take many years.”

The timing of the debate coincides with discussions about the future of the strategic nuclear deterrent. The UK Government will decide in 2016 on new submarines, in a programme known as the Successor Submarine Programme.

What is the Successor Submarine Programme?

The Successor is the replacement for the Vanguard submarines that carry the nuclear warheads and missiles. In light of the lengthy procurement process required for complex weapons systems, Parliament voted in 2007 to renew Trident. The 2010 Strategic Defence and Security Review concluded the nuclear deterrent should be retained but delayed Main Gate until 2016. Main Gate is when the decision is made to proceed with the project and comes at the end of the assessment phase. The Ministry of Defence's annual updates to Parliament on the Successor are available online: The United Kingdom's future nuclear deterrent: 2013 update to Parliament

The life of the Vanguard-class submarines has been extended and the first Successor submarine is expected to enter service in 2028. The current nuclear warheads will remain viable until the late 2030s and the decision on a replacement warhead is not needed until 2019.

What is the timeframe?

The Scottish Government has made it clear that it wants nuclear weapons removed from Scotland and discusses it at length in Scotland's Future. Specifically, the Government considers “securing the speediest safe withdrawal of nuclear weapons from Scotland” to be one of its five priorities for defence and favours removing Trident “within the first term of the Scottish Parliament following independence.” This suggests a timeframe of around 2020-21, assuming the first elections are held in 2016. However it adds that the withdrawal of Trident nuclear weapons and/or the Vanguard submarine fleet would be decided and delivered “as quickly as it can be both safely and responsibly secured.”

In Scotland analysis: Defence the UK Government suggests it would take many years to reproduce the current facilities at Faslane and Coulport elsewhere.

Where is Trident based?

The UK's nuclear deterrent is based in western Scotland at Her Majesty's Naval Base Clyde.

The submarines are based at Faslane on the Gareloch and the warheads are stored at the Royal Naval Armaments Depot, Coulport on Loch Long, accessible from the Irish Sea and North Atlantic.

Coulport has a covered floating explosives handling jetty from which warheads can be safely loaded on to, and unloaded from, on-board missiles using overhead cranes. No missiles are stored at Faslane or Coulport. Instead, by agreement with the United States, they are maintained and stored in King's Bay, Georgia, in the US. Coulport does have the ability to unload and store missiles in an emergency.

Warheads are designed, built and maintained at the Atomic Weapons Establishment (AWE) at Aldermaston, Berkshire.

Where could Trident go?

Relocating the nuclear deterrent is complicated because of the twin requirements of a suitable submarine base and a warheads depot that provide the same facilities currently provided by Coulport and adhere to safety requirements.

Professor Malcolm Chalmers, who studied the original decision in the 1960s as to where to base the nuclear fleet in his book Uncharted Waters, argues “relocation of these bases would be very difficult, if not impossible, to implement.” The House of Commons Scottish Affairs Committee looked at this question in detail in its enquiry The Referendum on Separation for Scotland: Terminating Trident – Days or Decades? The Committee concluded that “identifying and recreating a suitable base to replace Faslane and Coulport would be highly problematic, very expensive and fraught with political difficulties.” The Committee also explored, but ultimately dismissed, other proposals including negotiating the use of Faslane as a UK base within Scotland, or locating the deterrent outside the British Isles entirely.

The UK Government says it is not planning for Scottish independence and refuses to be drawn on possible alternative locations. Andrew Robathan, then Armed Forces Minister, said during a debate on Trident and the Scottish referendum “we do not have a better site” than the current one for the nuclear deterrent in the United Kingdom.

How much would relocation cost?

Although there are no exact estimates, the UK Government suggests in Scotland analysis: Defence that “any alternative solution would come at huge cost ... it would cost billions of pounds and take many years.” The then Armed Forces Minister Nick Harvey told the Scottish Affairs Committee it would “cost a gargantuan sum of money”.

Who would pay for the relocation and associated clean-up costs of the facilities in Scotland is also likely to be subject to negotiation.

Should the UK give up the nuclear deterrent?

The UK Government is committed to replacing the UK's nuclear deterrent and Parliament voted in 2007 in favour of the general principle that the UK should retain a strategic nuclear deterrent.

However there is significant opposition to the nuclear deterrent in Parliament. This ranges from outright opposition to its existence, to calls, led by the Liberal Democrats, for a change to the current posture. The Trident Alternatives Review study into the costs, feasibility and credibility of alternative systems and postures but not into whether the UK should have a nuclear deterrent was published in July 2013 (Library note Update on the Trident Successor Programme looks at the Review in detail).

The timing of this debate is important because the main investment decision for the Successor programme, known as Main Gate, is expected in late 2016. This is when a decision on the final number of submarines needed to maintain a continuous-at-sea presence will be taken. Members are already concerned about the considerable cost of the Successor programme in light of the current pressures on the defence budget. The additional cost of moving Trident out of Scotland to another location might only heighten those concerns.

The annual running costs for the nuclear deterrent, including the Atomic Weapons Establishment's costs, are between 5% and 6% of the defence budget. The Government set out its policy on the nuclear deterrent in a White Paper published in 2006: The future of the United Kingdom's nuclear deterrent. The White Paper estimated the costs of the Successor programme at £15 to £20 billion for the submarine, warhead and infrastructure. The Government says that current forecasts for the submarine alone indicate that the costs remain within the estimates made in the White Paper of £11 to £14 billion at 2006/07 prices.

Parliamentary action

The House of Commons Scottish Affairs Committee and Defence Committee have explored these questions in their inquiries on the referendum and Trident: The Referendum on Separation for Scotland: Terminating Trident – days or decades? and The Defence implications of Possible Scottish Independence respectively.

Members have discussed the question at length in a number of debates, including the Scottish Affairs select committee report in Westminster Hall on 7 March 2013, c317-362WH, on the nuclear non-proliferation treaty on 20 June 2013, c319-338WH, and the Trident Alternatives Review on 17 July 2013, c1219-1269.

Library research papers

A history of the British nuclear deterrent is available in House of Commons Library Research Paper The Future of the British Nuclear deterrent, 3 November 2006, RP06/53.

A more recent account of Trident is provided in House of Commons Library Standard Note Update on the Trident Successor Programme, SN06526 (latest update: 4 July 2014).

Reading material is collated in the Library bibliography The Future of the British Nuclear Deterrent: Suggested Reading, 13 August 2013, SN04207.

Article's author

  • Louisa Brooke-Holland
  • House of Commons Library

Page published: 12 June 2014

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This article was written in advance of the referendum, looking at the possibility of a Yes vote.

It provides useful context but some details may be overtaken by potential developments following the vote. It is retained for historical interest.