Britain’s ability to rely on the US to maintain the UK’s nuclear arsenal is now in doubt, experts have warned, but working with European states to replace it will be costly and take time.
An existing debate about the future of Trident – Britain’s ageing submarine-launched nuclear missile system – has taken a dramatic new turn in recent weeks amid fears Donald Trump could pull out of Nato.
A range of concerns had already loomed over the £3bn-a-year programme, not least around its efficiency and effectiveness after a second embarrassing failed test launch last year.
Costs have also been a longstanding challenge but replacing Vanguard submarines on time has been prioritised over coming in under budget.
Downing Street sought to play down concerns earlier this week after diplomatic figures including the former British ambassador to the US Sir David Manning floated the scenario of an end to Anglo-US nuclear cooperation.
However, calls for Britain to make alternative plans have been joined by the former UK foreign secretary Sir Malcolm Rifkind, who initiated talks in the 90s between the UK and France on nuclear weapons cooperation.
“It really is necessary for Britain and France to work more closely together because if American reliability ever came into question, then Europe could be defenceless in the face of Russian aggression,” he said.
“The contribution by America must now be to some degree in doubt, not today or tomorrow, but over the next few years and certainly as long as Trump and people like him are in control in Washington.”
A No 10 spokesperson insisted this week that Keir Starmer viewed the US as a reliable ally, saying: “The UK’s nuclear deterrent is completely operationally independent.”
Yet the UK is – unlike France – highly intertwined with the US when it comes to maintaining its nuclear weapons, which are designed, manufactured and maintained in the US under a deal rooted in a 1958 agreement. Britain had 50 missiles left as of 2008 after purchases from a US stockpile, according to research by the University of Bradford.
“Britain likes to call its nuclear posture independent, but it, of course, is absolutely not,” said Hans Kristensen, who monitors the status of nuclear forces for the Federation of American Scientists, a US thinktank.
“It may be that Britain can fire weapons independently of the US, but below that, the entire infrastructure covering missile compartments on submarines, the missiles themselves, all are supplied by the Americans.”
Defence analysts are emphasising the need to plan for a scenario where a transatlantic relationship fractures to the extent that the US declines to give the UK missiles.
Dr Marion Messmer, a senior research fellow at Chatham House and an expert on nuclear weapons policy, said: “It would be a big risk if it wasn’t being planned for, but it’s something the UK government can’t be too public about, as it wouldn’t want to give the Trump administration or Russia any ideas.”
Developing a replacement for Trident or adapting it for use without the US would be “hugely complicated” and costly, she emphasised, but added that ideas being floated included looking at ways for Britain to launch nuclear weapons by air rather than at sea.
“You wouldn’t necessarily be able to take the warheads which the UK uses for submarine launches and fit them for air launch. You would very likely need to develop a whole second warhead. That would require everything from new assembly facilities and workforce planning, but it could be a worthwhile investment for Britain,” she said.
“You could hope that France – the most obvious contender for Britain to work with – has a delivery vehicle similar to Trident that could easily be adapted, but it would require the French government and the French nuclear enterprise being willing to share those designs with the UK.”
Other factors are also coming in to play, including an openness by France’s president, Emmanuel Macron, to talks on extending its nuclear umbrella over the rest of Europe, and comments by Germany’s likely next chancellor, Friedrich Merz, that it could pay towards French and British nuclear costs.
Calvin Bailey, a Labour MP on parliament’s defence committee and a former RAF officer, said it was “difficult to conceive” of the US not wanting to maintain its relationship with the UK, stressing that this had been strengthened by the Aukus alliance between Australia, Britain and the US.
But he added: “We now also have to look at how we as Europeans ensure and guarantee our own safety and security. We’re showing leadership on this with the French, who are the most obvious partners for us.”
