Keir Starmer has sought to get into Donald Trump’s good books by boosting defence expenditure – and doing it in a very Maga way: slashing the UK aid budget to pay for it. That has no doubt caught the eye of the US president, as has the Prime Minister’s promise to put British boots on the ground in Ukraine as part of a European peacekeeping force after a deal is struck.
Mind you, that assumes that Vladimir Putin will keep to any deal to end the war. What if he doesn’t? Who guards the peacekeepers? Trump has made clear that European nations will have to look to their own security in future against an expansionist Russia. It’s not at all clear that America would send troops to stop Putin bullying, for example, the Baltic states, which have substantial Russian-speaking minority populations – or that President Trump would authorise the use of the full arsenal of US nuclear weapons against Russia if Putin delivered on his threat to use tactical nukes on the Ukraine battlefield.
Britain and France are the only nuclear powers in Europe capable of providing a credible deterrence to that threat. Germany wants the two nuclear nations to collaborate on an umbrella covering the whole of Europe. But just how independent is Britain’s independent nuclear deterrent?
The UK has command and control of these weapons, meaning that, in theory, we could launch the Trident missiles from any one of our four Vanguard nuclear submarines stationed at His Majesty’s Naval Base (HMNB) Clyde. The UK also controls the Royal Naval Armaments Depot (RNAD) Coulport, where warheads and missiles are stored for loading and unloading onto the submarines. One of these submarines is always at sea, providing what is called ‘continuous-at-sea deterrence’.
However, it’s not entirely clear that Britain could actually launch a nuclear war without the support of the US president. Our 50 Trident II D5 missiles are American and only leased by the UK. We collect them from a pool shared with the US at Kings Bay, Georgia, and they regularly return there for maintenance and upgrading.
The warheads are British, having been developed and maintained at the Atomic Weapons Establishment (AWE) Aldermaston – which used to be the target of annual Ban the Bomb marches half a century ago. However, developing them is a joint exercise with the US firm Lockheed Martin. The guidance systems are also American, as is the network of satellites that are essential for accurate targeting.
Would Donald Trump be happy with the UK threatening to use nuclear weapons against his new mate Vladimir Putin? The question has to be asked because there are any number of ways that a US president could prevent the UK using nuclear weapons, or undermine confidence that they could be used independently of US support. He could simply ask for ‘his’ missiles back, or refuse software updates to the targeting systems.
This all seemed rather academic in the past since it was assumed that Britain’s nukes would only be used as part of the North Atlantic Treaty Organisation (Nato). Under the Nassau Agreement of 1962 between John F. Kennedy and Harold Macmillan, Britain agreed to formally assign its nuclear forces to the defence of Nato, except in an ‘extreme national emergency’. No one bothered to ask what an extreme national emergency would look like since the weapons were there to deter the Soviet Union; no one thought Britain would go to war unilaterally.
All that has changed. There is now a hot war in Europe, during which Russia has made clear that it could use tactical nukes on the battlefield. It has deployed nuclear weapons in Belarus in defiance of the Nuclear Non-Proliferation Treaty. Europe now has a regional nuclear threat to contend with – just as the US appears to be withdrawing from Nato’s Article 5 commitment to declare war if any member state is attacked.
If Britain’s nuclear weapons are to provide the backstop that other European nations want, Keir Starmer is going to have to seek cast-iron guarantees – if such a thing is possible – that the UK’s nuclear weapons can retain US support come what may. During the cold war, politicians and commentators used to debate ‘whose finger’s on the button’. In 2025, it looks rather as if it is President Trump who controls the off switch.
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