House of Commons Library

Replacing the UK's 'Trident' Nuclear Deterrent

Published Monday, July 11, 2016

After nearly a decade of work on a programme to replace the UK's nuclear deterrent from the early 2030s, a decision on taking that programme forward will be made shortly. The Government will seek the approval of Parliament for this decision on 18 July 2016. But what are the arguments for and against doing so? How much will it cost? And are there any other alternatives? This paper updates and replaces all previous House of Commons Library briefing papers on this subject dating back to 2006. More notably it replaces previous versions of this paper published in October 2015, January 2016, March 2016 and June 2016. It is also part of a wider Library briefing series on nuclear weapons.

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In 2007 the Government, endorsed by a Parliamentary vote, began a programme to maintain the UK’s nuclear deterrent beyond the early 2030s. Under this programme the current Vanguard class ballistic missile submarines will be replaced (the Successor programme); while the UK will also participate in the current US service-life extension programme for the Trident II D5 missile, which will enable this missile to be deployed aboard the new submarines until the early 2040s.

Nearly a decade later a decision on taking the Successor programme forward into the manufacture phase is due to be taken. The Government will seek the approval of Parliament for this decision on 18 July 2016.

What is Trident?

Trident is the colloquial term used for the UK nuclear deterrent. The deterrent as a whole, however, comprises three main elements and has a vast supporting infrastructure:

  • Four Vanguard class submarines (SSBN) which maintain continuous at-sea deterrence (CASD), meaning that one vessel is always on patrol (Operation Relentless).
  • The Trident II D5 ballistic missile. The UK has title to 58 missile bodies, which are held in a communal pool at the Strategic Weapons Facility at the Kings Bay Submarine Base in Georgia, USA. Maintenance and in-service support of the missiles is undertaken at Kings Bay at periodic intervals.
  • Nuclear warhead. The infrastructure for building and maintaining the UK’s nuclear stockpile is located at two government-owned, contractor-operated Atomic Weapons Establishment (AWE) sites at Aldermaston and Burghfield in Berkshire.

The deterrent is based in western Scotland at HM Naval Base Clyde. The submarines are based at Faslane and the warheads are stored, processed and maintained at the Royal Naval Armaments Depot at Coulport. In-service maintenance of the Vanguard class is conducted at Faslane; while deep maintenance/refit is conducted at HM Naval Base Devonport in Plymouth.

Decision making on the use of British nuclear weapons is a sovereign matter for the UK. There is no requirement to gain the approval of the United States or other NATO allies for their use and only the Prime Minister can authorise an instruction to fire. 

By the time of the 1998 Strategic Defence Review (SDR) the majority of costs associated with procuring Trident had been spent. The SDR put total acquisition expenditure on the Trident programme at £12.52 billion, which equates to £18.35 billion in 2015-16 prices.

The decision to acquire Trident was announced in a Statement to the House in July 1980. A parliamentary debate, and vote, endorsing the Government’s decision was held in March 1981.

From the decision in 1980 it took 14 years to complete the acquisition of the Trident capability with the first Vanguard class submarine entering service in December 1994.

UK nuclear policy

The UK is signatory to a number of treaties and agreements relating to nuclear weapons and their delivery systems which confer several obligations on the UK with respect to its nuclear policies. The most significant are the disarmament obligations stated in Article VI of the Treaty on the Non-Proliferation on Nuclear Weapons (NPT). Under that article the five recognised nuclear weapon states are permitted to possess nuclear weapons, but only if they commit themselves to the principles of nuclear arms control and eventual disarmament. 

In 1996, the International Court of Justice also issued a non-binding advisory opinion on the legality of the threat or use of nuclear weapons. That advisory opinion concluded that “There exists an obligation to pursue in good faith and bring to a conclusion negotiations leading to nuclear disarmament in all its aspects under strict and effective international control”.

Successive governments have insisted that the UK’s nuclear deterrent is fully consistent with all of the UK’s international legal obligations. They have also expressed the belief that the current programme to replace the nuclear deterrent is compatible with the UK’s obligations under the NPT, arguing that the treaty contains no prohibition on updating existing weapons systems and gives no explicit timeframe for nuclear disarmament.

The UK has taken a number of steps since the end of the Cold War in support of the NPT. It has withdrawn all other nuclear weapons systems except for Trident; made changes to the operational status of the deterrent and been increasingly transparent about its nuclear inventory. By the mid-2020s the UK will have achieved a 65% reduction in the size of its overall nuclear stockpile, making it the smallest of all the NPT nuclear weapon states.

The 2015 Strategic Defence and Security Review (SDSR 15) confirmed that the “UK will not use, or threaten to use, nuclear weapons against any non-nuclear weapon state party to the NPT”. This assurance does not apply, however, to any state in material breach of the NPT. The UK also maintains a position of ambiguity on the precise details of when, how and at what scale the UK may consider the use of its nuclear weapons capability, although the Government has stated that nuclear weapons would only be used in extreme circumstances of self-defence.

Replacing the UK’s nuclear deterrent

The Labour Government’s 2006 White Paper, The Future of the United Kingdom’s Nuclear Deterrent concluded that the international security environment does not justify complete UK nuclear disarmament and that, in terms of both cost and capability, retaining the submarine-based Trident system would provide the most effective deterrent.

The decision was therefore taken to maintain the UK’s existing nuclear capability by replacing the Vanguard class submarines (SSBN) and participate in the current US service-life extension programme for the Trident II D5 missile.

A debate and vote in the House of Commons on the general principle of whether the UK should retain a strategic nuclear deterrent beyond the life of the current system was held on 14 March 2007. That motion was passed on division by 409 to 161 votes.

Although commonly referred to as “the renewal or replacement of Trident”, the Successor programme, is about the design, development and manufacture of a new class of four submarines. A Common Missile Compartment for the SSBN, which will house the current Trident strategic weapons system, is being developed in conjunction with the United States. Replacement of the Trident II D5 missile itself is not part of the Successor programme. Under changes introduced in the 2015 SDSR, the first SSBN is now expected to enter service in the early 2030s.

Decisions on a replacement warhead have been deferred until later this decade and it is expected that “no new significant infrastructure will be required to support the Successor submarines”.

The Successor programme is currently in a five-year assessment phase. Several long-lead items, including the specialised steel for the first submarine, have been purchased as part of assessment phase work. Manufacture of the submarines will not take place, however, until after the first main investment decision on this programme is taken later in 2016.

The 2015 SDSR confirmed that the costs of design and manufacture of a class of four SSBN, including inflation over the 20-year life of the programme, would be £31 billion, an increase of £6 billion on estimates set down in the programme’s Initial Gate report in 2011. A £10 billion contingency will also be set aside.

The Concept Phase of the programme had an allocated spend of £905 million, while the Assessment Phase, to 2016, now has an allocated budget of £3.9 billion. The years of peak expenditure are expected to be principally 2018 through to the mid/late 2030s, as the programme moves into full production.

Once the new nuclear deterrent submarine comes into service the annual in-service costs are expected to continue at approximately 6% of the defence budget, which, on current spending levels, is £2.3 billion per year. Calculating overall in-service costs, however, is fraught with difficulty as assumptions have to be made about the level of defence spending over the next 50-60 years.

In line with convention, the Successor programme will be funded from the MOD’s core equipment procurement budget.

Many believe the MOD’s assessment of cost to be under-estimated and that the true cost of replacing the nuclear deterrent will be much higher. CND’s most recent estimate in May 2016 has suggested that the cost of the replacement programme will be £205 billion, although this is over the 30-year life of the system and takes into consideration other potential costs, such as the cost of decommissioning. It also bases its in-service cost calculations on figures previously presented by Crispin Blunt MP, which made a number of assumptions about GDP growth over the next 50 years and that defence spending will continue to meet the NATO 2% of GDP target over this same period.

BAE Systems, Babcock International and Rolls Royce are the Tier One industrial partners in this project. As with previous SSBN, the submarine will be built by BAE Systems in Barrow-in-Furness and the PWR3 propulsion system will be built by Rolls Royce at Raynesway, Derby. The MOD has stated that maintaining and sustaining the UK’s nuclear deterrent supports over 30,000 UK jobs. Approximately 2,200 people across the MOD and all three companies are currently working on the Successor programme, of whom over 50% are engineers and designers. Jobs are expected to peak at 6,000 during the build phase and involve an estimated 850 British companies in the supply chain.

As one of the largest government investment programmes going forward, the 2015 SDSR announced that new organisational and managerial arrangements for the UK’s defence nuclear enterprise as a whole, and for delivering the Successor programme specifically, will be established. A new team within the MOD, headed by a commercial specialist, will oversee all aspects of the nuclear enterprise; while a new delivery body will be established in order to deliver the procurement and in-service support of all nuclear submarines, including Successor.

The 2015 SDSR also announced that new commercial arrangements would be put in place that will see the programme subject to several stages of investment, instead of the traditional single ‘Main Gate’ approach which entails a single investment decision. The next phase of the programme, which SDSR 15 refers to as “risk reduction and demonstration” will begin later in 2016.

The Government has stated that there will be a debate and a vote in Parliament on “the principle of continuous at-sea deterrence and our plans for Successor” on 18 July 2016.

Arguments for and against replacement

The UK’s status as a nuclear weapons state has always been a matter of contention and the current debate on renewal has, at its heart, all of the same fundamental arguments.

On the one hand there are those, including the Government, who advocate the UK remaining a nuclear power, in some form or another, citing the uncertainty of the strategic environment over the next 50 years. On the other, there are those who advocate disarmament and the move toward the UK becoming a non-nuclear weapon state.

Disarmament advocates argue that the UK’s nuclear deterrent should not be renewed on one or more of the following grounds:

  • Traditional notions of deterrence are no longer credible against non-state actors like al-Qaeda or more recently ISIS/Daesh; or in an age of ‘hybrid’/asymmetric warfare in which cyber attacks and drone operations are increasingly becoming the norm. Proponents of this view also argue that the evolution of underwater drone technologies and cyber capabilities could render submarine-based nuclear systems obsolete at some point in the future, and highly likely within the lifetime of Successor. 
  • Dispensing with nuclear weapons would serve as a positive example for other states to follow; would bolster the NPT regime and would enhance the UK’s authority and standing internationally.
  • In a period of financial austerity the money to be spent on a Trident replacement would be better spent on either improving the UK’s conventional military capabilities, in particular counter-terrorist and drone capabilities, or being put to greater use within the NHS or addressing issues such as environmental concerns, poverty, disease and debt.
  • Replacing the nuclear deterrent would breach customary international law and the UK’s disarmament obligations under Article VI of the NPT.
  • Retaining a nuclear deterrent should be condemned on moral grounds

Advocates of retaining the British nuclear deterrent predominantly argue that, while there is currently no direct threat to the UK, there is no way of predicting with any confidence the strategic environment over the next 40-50 years. Specifically:

  • The existence of non-state actors and rogue states with the intent and capability to develop weapons of mass destruction, coupled with the threat posed by the proliferation of nuclear knowledge and technology, make it imperative that nuclear weapons be retained.
  • In the coming decades a potential threat may emerge from an existing nuclear power that combines both the capability and intent to strike the UK. Some point to the growing military and economic power of China or the risk of future instability as a result of Russian adventurism.
  • There can be no guarantee that other aspiring nuclear weapon states or rogue states with nuclear intentions, such as North Korea, would give up their arsenals or plans purely because the UK has foregone its nuclear deterrent capability.

To supporters the deterrent therefore represents the ultimate security guarantee for the UK and they believe that the cost of retaining it is comparatively small when compared with the strategic risks of disarmament.

Alternatives to a like-for-like replacement

If one sets aside the argument for unilateral disarmament and accepts the assumption that the UK should remain a nuclear power, there are several schools of thought on alternatives to a like-for-like replacement.

Many view the replacement programme as a unique opportunity to either further the UK’s disarmament obligations or to make cost savings by pursuing other options. Such options include adopting a reduced nuclear posture (i.e. abandoning continuous at-sea deterrence); converting the existing system/replacement SSBN to a ‘dual use’ role; or the procurement of an entirely different system based either on a cruise missile system or an air-launched free-fall bomb.

Beyond that, there are also those who advocate the concept of a ‘virtual arsenal’ or threshold status for the UK whereby the UK disarms but retains the ability to reconstitute a nuclear capability within a matter of months or years, should it become in the national interest to do so.

The merits of any of these options are shaped by two fundamental premises:

  • The level of strategic risk one is prepared to take.
  • The financial burden one is willing to commit to.

As part of the Conservative/Liberal Democrat Coalition Agreement in May 2010 it was agreed that, while the programme would be scrutinised for value for money within the framework of the Strategic Defence and Security Review, the Liberal Democrats could continue to make the case for alternatives.

An unclassified version of the Trident Alternatives Review was subsequently published on 16 July 2013. While the review examined a number of alternative systems and postures, it concluded that, within the timeframe under consideration, an SSBN operating a continuous at-sea deterrent posture offered the UK the highest level of assurance that can be attained with a single deterrent system.

However the review went on to highlight that “there are alternative non-continuous postures that could be adopted”, although “none of these alternative systems and postures offers the same degree of resilience as the current posture of continuous at-sea deterrence, nor could they guarantee a prompt response in all circumstances”. The report also noted that any change to the UK’s deterrent system and/or posture could impact on the UK’s wider national interests and relations with allies.

Although supported by the Liberal Democrats, the review was met with widespread criticism from elsewhere across the House. Concern was largely expressed over the review’s suggestion that the UK could adopt a ‘part time’ deterrent, which many Members argued provided no deterrent capability at all, and the lack of consideration given in the report to the UK’s submarine manufacturing capabilities. A number of MPs even suggested that the outcome of the review had undermined the Liberal Democrats’ case for arguing for alternatives in the first place. Advocates for disarmament went even further to criticise the total absence from the review of the other alternative for the UK: unilateral disarmament.

Outside Parliament the Trident Alternatives Review met with equally mixed views. Questions were raised about the risks of adopting a non-continuous deterrent posture and whether moving forces to a higher readiness level during a crisis could be sustained with just a small fleet of submarines; whether breaks in patrolling could prompt a pre-emptive strike against inactive forces; and what effect an escalation in patrolling during a crisis could have on an adversary and whether it could in fact escalate a crisis as opposed to de-escalating one.

Public opinion on Trident

Pollsters do not routinely ask questions about Trident in political opinion polls. Questions about Trident tend to be included in opinion polls only at times when the nuclear deterrent is a subject of public debate, or when newspapers, political parties, or campaign groups specifically commission polls on the subject.

Because of the infrequency and variability of opinion poll questions on Trident it is hard to measure trends in the level of support for and opposition to Trident over time. Nevertheless, a review of the available opinion poll evidence does suggest that, broadly speaking, the British public is divided on the question of whether Trident should be renewed. However, the public’s views on Trident are nuanced and their responses to public opinion polls are sensitive to the wording and framing of the question they are asked.

Commons Briefing papers CBP-7353

Authors: Claire Mills; Oliver Hawkins

Topics: Armed forces, Arms control, Defence equipment and procurement, Defence policy

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