Prime Minister Keir Starmer recently boarded one of the UK's four nuclear-armed submarines for a photo call as part of his attempts to demonstrate the UK's defence capabilities as tensions with Russia continue.

However, Starmer faces a problem. The submarine, and the rest of the UK's nuclear fleet, is heavily reliant on the US as an operating partner. And at a time when the US becomes an increasingly unreliable partner under the leadership of an entirely transactional president, this is not ideal. The US can, if it chooses, effectively switch off the UK's nuclear deterrent.

British and US nuclear history is irrevocably interwoven. The US and UK cooperated on the Manhattan project, under the 1943 Quebec agreements and the 1944 Hyde Park aide memoire. This work generated the world's first nuclear weapons, which were deployed on Hiroshima and Nagasaki in 1945.

It also led to the first rupture. In 1946, the US classified UK citizens as "foreign" and prevented them from engaging in secret nuclear work. Collaboration with the UK immediately ceased.

The UK decided to develop its own arsenal of nuclear weapons. The successful detonation of the "Grapple Y" hydrogen bomb in April 1958 cemented its position as a thermonuclear power.

In the meantime, however, Russia's launch of the Sputnik satellite in 1957 had demonstrated the lethal reach of Soviet nuclear technology. This brought the US and UK back together as nuclear partners.

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Talks on how to counter the Russian threat became the foundation of an atomic partnership that endures to the present day. This mutual defence agreement, signed in 1958, has provided the UK with affordable access to the latest nuclear technology and a reliable western ally. The treaty has been amended and adapted over time to reflect changes in the US-UK working relationship and the two are now so entangled that it is very hard to leave the co-dependent relationship.

Both sides have benefited from security and protection, especially during the cold war. However, Trump's new "special relationship" with Russia's Vladimir Putin has reconfigured the global order of geopolitics.

Serious concerns are now being raised about the UK's nuclear capacity, given the unpredictability and potential unreliability of the new US administration. Trump could ignore or threaten to terminate the agreement in a show of power or contempt.

The UK's Trident nuclear deterrence programme consists of four Vanguard nuclear-powered and armed submarines. The UK has some autonomy, as it is operationally independent and controls the decision to launch.

However, it remains dependent on the US because the nuclear technologies at the heart of the Trident system are US designed and leased by Lockheed Martin - and there is no suitable alternative. The Trident system therefore relies on the US for support and maintenance.

The UK is currently in the process of upgrading the current system. But its options seem limited. If the US were to renege on its commitments, the UK would either have to produce its own weapons domestically, collaborate with France or Europe or disarm. Each scenario creates new issues for the UK. Manufacturing nuclear weapons from scratch in the UK, for example, would be a costly and protracted activity.

Technical collaboration with France seems the most plausible back-up option at the moment. The two countries already have a nuclear collaboration treaty in place. France has taken a similar submarine-based approach to deterrence as the UK and French president Emmanuel Macron has suggested its deterrent could be used to protect other European countries. Another alternative would be to spread the cost across Europe and create a European deterrence - but both strategies just re-embed the UK's current nuclear reliance.

While these weapons may deter a hostile nuclear strike, they have failed to prevent broader acts of aggression. Nuclear weapons have not been used in warfare for 80 years. Perhaps it is time to completely and permanently unshackle the UK from nuclear deterrence, and consider alternative forms of defence.

The UK's nuclear arsenal is expensive to maintain. The cost of replacing Trident is Pound 205 billion. In 2023, the Ministry of Defence reported that the anticipated costs for supporting the nuclear deterrent would exceed its budget by Pound 7.9 billion over the next ten years. This funding could be channelled into more pressing security threats, such as cybersecurity, terrorism or climate change.

Nuclear weapons will become strategically redundant if the UK cannot act independently. As Nato and the US dominate the global nuclear stage, the UK's capacity to respond has become contested. The time has come to decide whether the US is really our friend - or a new foe.