Trident is in the manifesto – now Corbyn faces a major test in how to explain it

There is little doubt that Jeremy Corbyn’s personal commitment to unilateral nuclear disarmament will be attacked over the next few weeks. Now we know, however, that the draft manifesto pledges to renewing Trident while Labour continues to pursue multilateral nuclear disarmament.

This, after all, is party policy as determined by conference. The problem for Labour is how to explain the apparent divergence between party policy and the personal views of the leader of the party.

So what does the leadership say about this over the next few weeks? Labour policy is to retain the nuclear deterrent which requires a Labour government to maintain a continuous at sea presence of at least one Trident submarine.

What has changed under Corbyn is that there is a much stronger commitment to seeking a nuclear weapons free world through UN talks. The leaked manifesto underlined this when it said a Labour government would “lead multilateral efforts with international partners and the UN to create a nuclear free world”.

It is unclear whether Corbyn, if he became prime minister, would try to order the submarines back to the UK and disarm them. If he did, he may find that a majority of his MPs, and possibly his cabinet, opposing that decision. He would be accused of betraying a Labour manifesto commitment and could face a vote of no confidence in parliament. Those voters who had supported the party’s policy of multi-lateral disarmament and backed Labour on that basis would find it very hard to ever trust the party again. It is therefore highly unlikely that prime minister Corbyn would try to stop Trident from patrolling. He would be in direct contravention of party policy and its manifesto.

A more difficult question is what impact his personal views would have on the potential use of Trident. One of the first requests made by officials to an incoming prime minister is to write a letter of last resort for the commanders of the UK’s Trident fleet instructing them on what to do in the event of a nuclear conflict which has destroyed the British government. This letter is always kept secret to ensure that a potential adversary cannot predict the precise nature of the UK’s response. Presumably that is also why no one apart from the PM is supposed to know the contents of the letter. As there is no clear party political or official policy guidance on what should be in this letter it can be assumed that each occupant of No 10 is guided by his or her own personal views.

What is also clear is that this request is not governed by statue or any specific regulation. It is – like so many other aspects of the prime minister’s role – a matter of convention. We already know that Corbyn has said that he would never authorise the use of nuclear weapons under any circumstances. However this position fatally undermines the purpose of the nuclear deterrent. There is no point in having Trident if everyone knows that in extremis the order will never be given. So given Corbyn’s personal views on this is there a case for changing the convention? Why does he personally have to write the letter? Couldn’t he transfer this responsibility to another senior member of the Cabinet? What impact would such changes have on the UK’s deterrence policy?

The key to an effective deterrence policy is to ensure that our adversaries are sufficiently uncertain about our response to a nuclear attack. If they believe there is a significant risk that, despite his own personal preferences, a Corbyn-led government would use Trident then a credible deterrence position will have been maintained.

Nevertheless the Labour leadership face a big challenge in persuading potential voters that the Trident policy of a Corbyn administration is credible. Currently Labour policy is one of keeping the deterrent but exerting much greater diplomatic pressure to achieve a nuclear weapon free world. This has been an objective of successive British governments since the signing of the 1970 non-proliferation treaty. It is evident that in the last 47 years very limited progress has been made.

Therefore there is an opportunity for an incoming Labour to push this issue far higher up the international agenda. This in no way contradicts Labour Party policy of supporting the retention of a viable UK nuclear deterrent until a nuclear-free world has been reached. That policy has to be credible and remain credible as it comes under attack from Labour’s critics in the coming weeks.

Corbyn has always had a principled attachment to unilateralism. However he has also always said that politics is about policy, not personalities. He is the leader of a party that has a clear policy that he personally disagrees with. The manifesto leak shows how he has tried to reconcile his own personal views with the policy of the party he leads. It is a test that the Daily Mail, the Conservative Party and many others will claim he has already failed. Despite this the only audience he is interested in is the British electorate. What he decides to say to them over the coming weeks is one of the most difficult challenges he will face.

Josh Arnold-Forster is a political consultant. He worked for John Reid during his time as defence secretary and for Martin O’Neill and David Clark, who both held the brief in opposition.