Britain doesn’t need a new nuclear deterrent: It needs a better one

 Last week, before party members gathered at the Liberal Democrats’ spring conference in York, Sir Ed Davey, leader of the Liberal Democrats, called for the UK to rethink its nuclear deterrent.

His argument was clear: while Britain should continue to rely on Trident in the near term, it ought to begin building a fully sovereign nuclear capability to replace it by the 2040s, ending our dependence on the United States.

Considering the mercurial nature of Donald Trump’s administration, many will agree that he was right to draw attention to this matter.

Davey was also right to point out that the UK’s deterrent relies heavily on US support. Although the UK manufactures its own nuclear warheads and submarines, it leases the Trident missiles to ensure its warheads can reach their targets. These are held in a common pool in the US and loaded on to Royal Navy submarines.

It’s important to stress that reliance is not control. The decision to fire Trident missiles rests with the Prime Minister – nobody can intervene once the UK makes the decision to launch.

Continuous at-sea deployment of nuclear-powered ballistic missile submarines remains the most credible, survivable and effective deterrent. It underpins Britain’s global standing and provides the ultimate guarantee of national security.

There is a strong case for ensuring that the system is entirely domestically produced.

However, doing so risks diluting the “certainty” of the UK’s deterrent at a time of profound global instability. Walking away from a system built over decades would undermine Britain’s security, not enhance it. Focusing on replacing Trident, therefore, risks answering the wrong question.

The UK’s deterrence problem is immediate, not hypothetical. The challenge is not what might happen in the 2040s but whether the UK deterrent remains credible in the years ahead – when adversaries like Russia and China are becoming more aggressive.

Spending decades chasing a replacement would only distract from the urgent need to shore up our current capabilities.

The real issue is not sovereignty, but flexibility of response. Since the late 1990s, the UK has lacked sub-strategic nuclear options: the capabilities that allow states to signal intent, escalate proportionately and strike military targets without resorting to full-scale, strategic nuclear use. Without them, deterrence becomes blunt and difficult to apply outside an existential threat.

The problem is not Trident itself, it is that Trident is all that Britain has.

The strategic landscape is now shifting. Across Europe, nuclear questions have returned to the centre of defence policy. The Kremlin is seen to be deliberately undermining regional stability through explicit nuclear coercion, while some European governments are discussing gaining their own weapons.

The recent offer of “forward deterrence” from French president Emmanuel Macron – although more dressing than substance – reflected a renewed focus on escalation and nuclear signalling.

The UK sits awkwardly within this environment. It is one of only two nuclear Nato powers in Europe, yet, unlike France, its deterrent is highly rigid – a problem that is becoming more and more acute.

Besides its strategic nuclear force, France still possesses sub-strategic nuclear forces that it can fire from aircraft. These smaller nuclear weapons allow France to fire a warning shot in the event of escalation, ostensibly to prevent a full exchange. This provides greater flexibility and security.

Britain’s conventional forces are also under pressure, with naval capacity and personnel both in decline. Rebuilding will take time and sustained investment. During that period, nuclear forces will carry a greater share of the burden, yet the UK still lacks credible options between conventional force and full-scale nuclear escalation.

Rebuilding the missing rungs on the escalation ladder is the central challenge for the UK’s defence policy, not whether Britain’s strategic deterrent should be fully independent by the 2040s.

Every pound diverted into making Trident fully sovereign is a pound not spent on rebuilding conventional strengths or developing a sub-strategic nuclear capability. In a future crisis, the choice may therefore be stark: absorb an attack or escalate to strategic nuclear use. This is not a credible deterrent posture.

Initially, a British sub-strategic nuclear force could involve more F-35As armed with a British nuclear bomb or missile, but later, it could employ the Tempest airframe being developed under the Global Combat Air Programme, which is expected to deliver a sixth-generation combat aircraft (or a combination of both aircraft).

A sub-strategic nuclear capability would not be cheap, but it is a far more timely and relevant response. It addresses the gap that the UK faces now rather than a hypothetical one in the future, while also enhancing sovereign control and options.

Davey is right that the UK must think seriously about its nuclear future, but full independence is not the priority. Credible deterrence is. This requires a sub-strategic nuclear deterrent, delivered at speed and at the lowest possible cost.