Sir Bernard Jenkin was Shadow Defence Secretary (2001-3), a member of the Defence Select Committee (2006-10), and regularly speaks and writes on defence policy.

The Integrated Review (IR) of defence, foreign and security policy, included a surprise announcement – to abandon the 2010 target of reducing the number of nuclear warheads to 180 “by the mid-2020’s”, and instead to raise it to 260.

This was denounced by the established unilateralists, but it also raised eyebrows amongst many who support our Continuous At Sea Deterrent (CASD), and the Vanguard submarine replacement programme.  They carry the Trident intercontinental ballistic missiles (ICBMs).

The decision to approve the construction of four new Dreadnaught nuclear submarines was finally taken in 2016 by 472 votes to 117, despite the fact that the then leader of the Labour Party was a dedicated member of CND.

That result underlined the remarkable strength of the bipartisan consensus in favour of the maintenance of CASD for the next 50 years.  It also underpinned confidence.  This challenging technological and engineering programme requires substantial political certainty.

Raising the cap on the number of warheads has shaken some, who assumed that the UK would continue to reduce its nuclear capability, even if this amounts to unilateral disarmament.  Indeed, the 2010 intention to reduce the cap appears to have been a condition of the Liberal Democrat tolerance of CASD in the coalition.  That element of consensus has been cast out by the IR.

The Government could do more to explain this.  Since the Dreadnaught ‘main gate’ decision in 2016, the potential adversaries of the West have not been disarming.

The IR notes an increase in ‘great power competition’ from Russia (the ‘most accute’ threat) and China.  In terms of warheads, while we have something like 215 ready at this time, the US has “around 3,800 active warheads in the stockpile and another 2,000 retired warheads awaiting dismantlement.” Russia has “approximately 6,400 nuclear warheads—the largest stockpile of nuclear weapons in the world”.

Vladimir Putin has embarked on a substantial modernisation of its strategic and tactical nuclear weapons capability, and has developed a new nuclear tipped torpedo.  Russia has also continued developing missile defences which might threaten the certainty of an effective strike by our very limited single ballistic missile system.

China has a modest 350 warheads, and a policy of no first use, but this disguises what else they are doing.  China has developed a modern, complete range of delivery systems, from land-based ICBMs, through intermediate, medium and short range ballistic missiles, land attack nuclear missiles and the new Jin-class submarine based ICBM.  The DF-26 is a dual-capable missile system is capable of “hot-swapping” conventional and nuclear warheads.

This payload ambiguity is a feature – not a bug – for Chinese leaders seeking to manipulate risk in a crisis and thereby to enhance deterrence; but it could also amplify escalatory incentives in a crisis. China represents nothing like the immediate threat of Russia, but it is not disarming.

Then there is the proliferation amongst new potential adversaries, such as North Korea and Iran. Despite all the efforts, we must assume that they will become nuclear powers.

It is always tempting to say that our deterrent seems a very expensive minnow in all this.  We are in danger of seeing a re-run of all the failed arguments in favour of something even more limited and cheaper, or no deterrent at all, but the arguments for the UK’s CASD remain overwhelming.

It is by far the cheapest available option and for what it provides in terms of protection and UK global influence, it is extraordinarily good value.  The House of Commons Library reported last month that, in 2020-21, the estimated cost of maintaining the nuclear deterrent was around one per cent of total planned Government expenditure on UK social security and tax credits expenditure in that year. The increase in the warhead cap seems unlikely to add anything to the cost, since it is more just a recognition of reality: that the 180 cap by “the mid-2020’s” was never a realistic goal.

Peaceful and responsible defence is founded on the concept of deterrence.  Deterrence works because a potential aggressor can calculate that the cost of aggression will far outweigh any possible gains from that aggression.  To sustain deterrence, it is necessary to possess the means to inflict that cost on the potential aggressor.  For deterrence to be credible, it must be technically, logistically, and politically possible to deploy the means of deterrence.

State-on-state warfare, which dominated in the nineteenth and in the first half of the twentieth century, is often today dismissed as a low threat, so therefore people claim deterrence is an outdated concept.  However, human nature has not changed.  It is only the deterrent effect of nations’ arsenals of weaponry and armed forces that has made prospect of massively destructive state-on-state warfare unthinkable.

People often claim that nuclear deterrence is irrelevant to newer threats such as terrorism, biological and chemical weapons from rogue states and cyber warfare.  These are not existential threats.  However, the nuclear deterrent underpins all deterrence against known and unknown threats.  To give up the UK’s nuclear weapons capability would be to assume that future threats are predictable, which they are not.

Our CASD can be used at any time against any target in the world and is therefore always ready to respond to threats.  Its location is unknown, so it cannot be pre-empted or neutralised by a potential aggressor.  It does not require to be deployed at a time of international tension or crisis, so it is non-escalatory.  The technology is well-established and tried and tested.  Maintenance and renewal of the Trident-based CASD complies with the Nuclear Non-Proliferation Treaty (NPT). The UK’s CASD is a sovereign British capability requiring no other nation’s permission or technical support for its operation or sustainment.  The warheads are British.  No alternative system can achieve these aims.