Sometimes you can understand the rationale for a political decision even if you don’t agree with it. But when it comes to Boris Johnson’s decision to increase Britain’s nuclear arsenal—published in the government’s new Integrated Review—I struggled to get the thinking behind it.

Britain’s arsenal today stands at around 200 nuclear warheads. Each is about eight times the power of the Hiroshima bomb which killed over 200,000 people. That’s a killing capacity of hundreds of millions. How can Johnson conceivably justify that arsenal, never mind wanting to increase it?

Since the end of the Cold War, Britain has managed a gradual reduction in its nuclear arsenal, a trend continued by the last two Conservative governments; in 2010, David Cameron announced the current round of reductions which aimed to bring the number down to 180 by the mid-2020s. Presumably that work will now stop.

Britain’s reductions have not been out of the ordinary. In fact, they have been in line with a drop in the global figures from around 70,000 in the 1980s to around 14,000 today. The overwhelming majority of today’s nuclear warheads belong to the US and Russia, and most of these aren’t deployed. What’s more, last month Presidents Biden and Putin renewed the New START Treaty – the bilateral nuclear reductions treaty, which continues their downwards trajectory.

For a while, former President Trump had put the future of this agreement in doubt – but Biden made its renewal a priority when he entered the White House.

The problem we have been facing with nuclear weapons has largely been the modernisation programmes of the nuclear weapons states, rather than an increase in numbers. Britain has been modernising via the replacement of Trident, Britain’s second post-Cold War nuclear weapons system.

These modernisations are problematic in themselves because they always come with advanced capability – but the emphasis across nuclear weapons states has been replacing old kit rather than increasing stockpiles. So why is Johnson going against the global flow and increasing Britain’s arsenal? It’s as if he’s stuck in a Trumpian space when the show has moved on, unilaterally starting a new nuclear arms race.

One of the key questions posed to me by the media since the news of the increase was leaked has been this: is it legal? The answer is a clear no. Increasing Britain’s nuclear arsenal contravenes our legal obligations under the nuclear Non-Proliferation Treaty (NPT), which Britain ratified in 1970. The Treaty basically requires countries that have nuclear weapons to disarm, and those that don’t have them not to get them.

In fact when Blair’s government was first pursuing Trident replacement in 2005, Matrix Chambers gave a legal opinion which found that the replacement of Trident would be a material breach of the Treaty because it requires that ‘each of the parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament.’

Bizarrely, British governments always assert their unflinching commitment to the NPT, and the Integrated Review is no exception. It states: ‘We are strongly committed to full implementation of the NPT in all its aspects, including nuclear disarmament.’

Sadly, that’s just not true. Indeed our government—with all its Review’s talk of the ‘rules-based order’, the super-soft power of the BBC, its leadership in diplomacy—has just fired a Trident missile through its legal obligations and racheted up global tensions, presumably to reinforce Johnson’s image of a ‘global Britain’, punching above its weight and being a force in the world.

The Review is also quick to assert that ‘there is no credible alternative route to nuclear disarmament’ other than the NPT. This is a thinly-veiled reference to the government’s hostility to the UN’s new Treaty on the Prohibition of Nuclear Weapons, which I wrote about in Tribune when it came into force in January.

The government’s decision to increase its nuclear arsenal very clearly demonstrates why so many countries—largely those in the Global South—have given up hope in the NPT process, which has been rendered meaningless by the actions of states such as ours.

Johnson’s decision to increase Britain’s nuclear arsenal is a serious problem. It’s not just that we would rather the money was spent on something more useful, or that this flagrant breach of the NPT may encourage others to pursue nuclear weapons; it’s a question of what kind of world we want to see, what role we want Britain to play, and what it actually stands for. Rearming with weapons of mass destruction is not something that we can accept.

We must find it in ourselves to reject the dangerous humbug the government spouts about nuclear weapons – specifically, their claim that ‘the UK will continue to work internationally to reduce the risk of nuclear conflict and enhance mutual trust and security.’

This is nonsense, and we know it. I urge everyone to join CND and get active before this gets out of hand.