Chandigarh: The return of an impulsive Donald Trump to the US presidency has triggered quiet unease in London in recent months, over the resilience of Britain’s nuclear deterrent, as the Trident II D5 submarine launched ballistic missiles (SLBMs), responsible for delivering its warheads are not British-owned, but simply leased from Washington.“With an unpredictable and increasingly erratic US President in the White House, Whitehall is growing nervous about Britain’s dependence on America for its nuclear arsenal,” the UK’s popular Sunday Observer reported earlier this week.In her March 11 column, Rachel Sylvester highlighted how Trump had publicly humiliated UK Prime Minister Keir Starmer recently, over his refusal to full-heartedly back military action in Iran. Besides, the Greenland debacle, she said had cast fresh doubt over whether a shared alliance of values still prevailed between London and Washington – a situation that could directly jeopardise the over half-century-old SLBM deal.At the heart of this anxiety lies a little-discussed, strikingly ironic and perversely awkward truth: Britain does not own the missiles responsible for delivering its indigenously developed nuclear warheads. And, for 52 years, the UK’s most powerful instruments of national security have effectively been leased from the US in an arrangement rooted in the celebrated Anglo-American “special relationship” dating back to the Second World War. But it is also an alliance that lays bare a borrowed capability, which successive British prime ministers have nevertheless hailed as the “independent bedrock” of the nation’s strategic stability and global power projection.Britain designs and builds its nuclear-powered ballistic missile submarines (SSBNs) and manufactures warheads at the Atomic Weapons Establishment, but relies on Lockheed Martin–built Trident II D5 SLBMs to project its strategic deterrent worldwide. These missiles are stored, maintained and serviced at the US Naval Submarine Base at Kings Bay in Georgia, from which they are drawn whenever Royal Navy (RN) SSBNs require them for operational patrols.This SLBM leasing arrangement is unique among the world’s nine nuclear weapon states, making Britain the only power dependent on what is effectively a rental system for its or its core nuclear arsenal. The other eight – China, France, India, Israel, North Korea, Pakistan, Russia and the United States itself – retain full sovereign control over both their strategic warheads and the delivery systems, both designed and series built domestically, to carry them.Senior British officials and analysts have therefore, as reported by The Observer, begun voicing concern over the continued reliance on this unusually structured arrangement amid the ‘uncertainty’ and skittishness surrounding the current US administration. According to Sylvester the issue has acquired additional significance after Starmer’s Labour Party-led government had effectively “doubled down” on the UK-US collaboration soon after taking office in 2024. Defence Secretary John Healey, she stated, had tabled an amendment to the UK–US Mutual Defence Agreement – the pact governing the transfer of nuclear materials, technology and information – removing the earlier requirement that key provisions be renewed every decade.his extraordinary SLBM leasing arrangement dates back to the early Cold War and the Nassau Agreement of December 1962, when Prime Minister Harold Macmillan secured from President John F. Kennedy the right for Britain to access Polaris systems manufactured by Lockheed Missiles and Space Division – later Lockheed Martin. The 1963 Polaris Sales Agreement leased Britain the Polaris A-3 (UGM-27) SLBMs, with a 4,500 km range, giving the illusion of providing it an ‘independent’ nuclear capability, while in reality making London entirely dependent on Washington for the missiles that constituted the core of its strategic deterrent. From 1968, these missiles were installed on four RN Resolution-class SSBNs, purpose built to carry the leased Polaris systems.In the 1990s, the three-stage, solid-fuelled Trident II D5 SLBM, with a 7,400 km strike range, replaced Polaris, and was duly deployed aboard four Vanguard-class SSBNs that succeeded the earlier Resolution-class fleet, under a similar lease agreement. The four next-generation Dreadnought-class SSBNs, are currently under construction by BAE Systems at Barrow-in-Furness in northwest England and are due to join the fleet in the coming years. Like the Vanguard class, they too are engineered specifically to carry Trident, continuing the RNs dependence on US nuclear missile delivery systems production, maintenance, and logistical support.This reliance also shapes Britain’s Continuous At-Sea Deterrence, under which one of four Vanguard-class SSBN, armed with 16 Trident missiles, is on constant patrol. Collectively, these SSBNs maintain an uninterrupted nuclear presence at sea, projecting the appearance of strategic independence, even though the operational heart of Britain’s atomic arsenal remains hopelessly reliant on the US for its missile delivery capability.Meanwhile, Darya Dolzikova, senior research fellow at the Royal United Services Institute (RUSI) in London, questioned the true independence of Britain’s strategic deterrent. She told The Observer that because the UK leases the Trident missiles, the US could hypothetically terminate the agreement at will and stop supplying them.Ben Judah, former special adviser to Britain’s Foreign Ministry, similarly argued that London faced an “America problem” over the Trident missiles. “Our closest ally, around which we have built our entire security, has become profoundly erratic, unpredictable, and emotional,” he told The Observer. Judah added that if he were still in government, he would urge Britain to begin diversifying its strategic option by establishing a “new nuclear special relationship with France”, as a potential alternative to its current missile dependence on Washington.The underlying difficulty, however, in seeking an alternative missile system remains financial. As Sylvester noted in The Observer, the UK Defence Ministry’s budget was overstretched, preventing Britain from affording the development of a fully indigenous nuclear SLBM system, even if it were technically feasible. Replacing Trident with a domestic alternative, she added, would be prohibitively expensive and a decades-long endeavour – effectively forcing Britain into a permanent reliance on the US for the missiles that underpinned its nuclear strike capability.Supporters of Britain’s nuclear arrangement with the US argue that its deterrent remains operationally independent, as the ultimate decision to use nuclear weapons rests solely with the British prime minister. They maintained that in command and control terms, no external authority was required once the missiles were deployed aboard an RN SSBN on patrol.But critics argued that independence at the moment of launch tells only part of the story. They cautioned that, in practice, the credibility of Britain’s nuclear deterrent depended on a ‘functioning relationship’ with Washington, which was increasingly uncertain under Trump’s leadership. And, in the event that access to the shared Trident missile pool were ever withdrawn, the UK could well find itself without the means to sustain its nuclear deterrent.Following the 1998 Strategic Defence Review, Britain’s nuclear deterrent became exclusively submarine-based. During the Cold War, the UK had, alongside its SSBNs, maintained an airborne nuclear capability through the RAF’s V-bomber force – Vulcan, Victor, and Valiant – and later Tornado GR1 aircraft armed with WE.177 free-fall nuclear bombs. However, the retirement of these aerial platforms left the RNs four SSBNs as the sole means of sustaining the UK’s strategic nuclear deterrent.Meanwhile, few rituals in any nuclear-armed state capture the burden of command as starkly and somewhat eccentrically as the British prime minister’s first-day task of penning four secret “letters of last resort” to the commanders of the RN SSBNs. Within hours of taking office, the prime minister receives the launch codes for Britain’s nuclear arsenal and prepares four identical handwritten instructions for each of the SSBN captains, mandating the course of action should an atomic strike annihilate the government.The letters’ contents are known only to the serving prime minister and are sealed aboard the submarines, to be opened only if London’s chain of command was obliterated. When the prime minister leaves office, the letters are destroyed unopened, replaced with those written by his or her successor.In conclusion, even as the UK prime minister exercises ultimate authority on paper, its execution depends entirely on leased Trident missiles, highlighting the paradox that Britain’s supposed strategic independence rests on its hoary relationship with Washington, whose steadfastness no longer seems as certain as it once did.