Skip to main content

Verification, irreversibility and the road to nuclear disarmament

UN7911893 UN Emblem

By Mark Smith, Wilton Park Senior Programme Director

Last week, leaders of the G7 countries gathered in Hiroshima, site of the first use of nuclear weapons in 1945, for their annual Summit. It was, as the Summit’s Communique noted, the first such statement to have a particular focus on nuclear disarmament, and G7 members reaffirmed “our commitment to achieving a world without nuclear weapons with undiminished security for all”.

How is that nuclear weapon-free world to be achieved? In March this year, working in partnership with the UK and Norway, Wilton Park convened a pair of dialogues on two closely-interlinked issues for nuclear disarmament and the wider NPT regime: verification and irreversibility. These topics can trace their importance to the Treaty back to the Action Plan agreed at the 2010 Review Conference, which established three key principles of disarmament: transparency, verification and irreversibility.

Ambassador Aidan Liddle of the FCDO, in a blogpost on Wilton Park’s first dialogue on irreversibility in 2022, highlighted the interlink between the three: ‘You can’t tell whether what’s been done is irreversible unless you can verify it; you can’t verify it unless it’s transparent’.

In other words, multilateral disarmament needs to meet these three criteria if it is to be effective and resilient. However, verification and irreversibility in particular were under-explored in terms of how they would actually work in practice.

Although it might be thought that working on verifying disarmament and exploring what irreversibility might entail are redundant when nuclear numbers appear to be rising and nuclear threats are at a heightened level over Ukraine, the work is in fact of key importance.

At some point in the future, when current trends have shifted, the kind of work that is being undertaken now will come into its own. We’ll need to know in detail how to verify disarmament, and what a world irreversibly free of nuclear weapons actually looks like. Neither is this solely a long-term issue: current and very pressing debates about the North Korean nuclear programme, and nuclear arms control between the US and Russia, regularly reference both verification and irreversibility.


The UK and Norway were exceptionally well-placed to pick up the ball on verification, as they had already established a ground-breaking project investigating the technical and procedural challenges involved. After the 2015 RevCon  the UK and Norway led a UN Resolution establishing a Group of Governmental Experts (GGE) to investigate the verification issue and prepare a report for the Secretary General.

Wilton Park’s involvement with the verification issue began in 2018 when the FCDO and the Norwegian MFA asked us to convene a dialogue in support of the Group of Governmental Expert’s (GGE’s) first formal meeting.

GGEs typically run three formal meetings before submitting their report to the SecGen, and finding non-formal margins such as the WP meetings where they can continue to engage non-government experts, brainstorm, and lay the ground for the Chair’s report, becomes highly valuable.

We met first in January 2018, with the aim being to prime the pump: introduce GGE members to each other, assess their different takes on the verification issue, and go over the Norwegian Chair’s proposed plans for its work. This ensured that when they met at the UN in Geneva, they were ready to hit the ground running.

The dialogue was sufficiently successful that the Norwegian GGE Chair asked us to convene a second WP event, this time a this time a GGE members-only event at which he presented his first draft of the Group’s final report.

This model was repeated for the second GGE that continued the UN’s work on verification: the pump-priming meeting had to be held virtually, due to Covid restrictions, but the conference to review the Chair’s initial draft was fully in-person and nearly all GGE members joined us to go over each section of the report, offering their feedback to the Chair on what worked and did not work in the paper he submitted.

Wilton Park has therefore been closely supportive of both rounds of the UN GGE, and we remain ready to continue this relationship in whatever form international policy work takes after the current GGE concludes.


Irreversibility has remained the under-analysed part of the disarmament trio, a term used rather more often that it’s defined. Amid growing recognition in the NPT of this lacuna, we convened a dialogue in March 2022  to explore it further, a successful meeting that the UK and Norwegian partners used as the source material for their side-event at the NPT’s Covid-delayed Review Conference last August.

The draft Final Document there set out the widely-shared view that ‘further work is required to ensure the irreversibility of nuclear disarmament’ and called for States Parties to work on developing the concept.

It’s worth noting that irreversibility does not only apply in the context of the NPT’s ultimate goal of a nuclear weapon-free world, but has immediate applications too: the draft Final Document also called for ‘complete, verifiable, and irreversible denuclearisation of the Korean Peninsula’, and for the US and Russia to re-commit to ‘deeper, irreversible and verifiable reductions in their nuclear arsenals’. Hence this concept requires further work for contemporary security issues as well as laying the ground for the future.

We took up the baton from the Review Conference, and this Spring convened our convened our second dialogue on irreversibility, again with the UK and Norway as our partners.

At this dialogue we drew on a set of research papers funded by the UK FCDO and commissioned by King’s College London, written by an international team of experts. The key aim was to assess how to progress the concept of irreversibility in policy and academic/thinktank work, building on the previous event’s work on fleshing out its various aspects to provide an intellectual underpinning for future policy development

What now for these twin tracks of work? For international policy, the next stop is the NPT PrepCom in August. This is the first of three annual meetings leading up to the next Review, at which the GGE’s final report will be submitted and the UK and Norway will likely showcase their work on advancing the concept of irreversibility.

And for Wilton Park? We are uniquely placed to host these dialogues, given our role as neutral convenors and our network in the global NPT community. We will revisit both themes, and how they landed at the PrepCom, at our annual December dialogue in support of NPT diplomacy. We have also scheduled a third iteration of the irreversibility conference for March 2024, with support from the UK and hopefully Norway.

While current talk around nuclear threat may be heightened, this collaborative, painstaking work continues behind the scenes without headlines or fanfare.  Aidan Liddle tells us: “Wilton Park offers a unique venue for these sorts of discussions. Their convening power and knowledge of the subject matter means we can get the right people – from States and academia – in the room for a deep and candid discussion that can really move us forward.”

At Wilton Park, we’re proud to be part of a conversation aimed at making the world a safer place.

Want to find out more?

Sign up to our newsletter