It is a cliché that the UK's independent nuclear deterrent is neither independent nor a deterrent. It is de facto a part of the US nuclear arsenal and a symbol of the UK's status as a protectorate, which has been obvious since the commitment to Polaris in 1962. The deterrent to any possible enemies today or in the future is not Trident but the likelihood that an attack will prompt immediate retaliation by the US. This effectively puts us in the same category as those states who "share" American nuclear weapons as part of NATO's operational deployment (i.e. they possess missiles and bombs that can only be armed by the US), namely Germany, Belgium, The Netherlands, Italy and Turkey. We could not unilaterally use our nuclear weapons, for fear of an American countermand that would reveal our dependence (i.e. Suez all over again), while the idea of taking a raincheck in the event of a nuclear war involving the US is ruled out by membership of NATO. This means that Trident is militarily worthless - we can't use it when we wish and when we do it will be marginal to a larger conflict - which is why some of the system's most trenchant critics are to be found among the upper echelons of the army and airforce.
Any debate about Trident renewal or the prospect of unilateral nuclear disarmament is therefore a political debate, not a technical argument about the best way of ensuring national security. Just as weapons systems have always been ideological, from the property qualifications of hoplites to the concentration of capital of aircraft carriers, they also reflect the historically-conditioned concerns of elites. The maritime nature of the UK's nuclear strikeforce is a case in point. The fact that we are the only nuclear state wholly dependent on a submarine-based missile system is the product of a fear of the people rather than an eccentric belief that we should "rule the waves". Britain has traditionally minimised its standing army at "home", reflecting a suspicion of agitators and a fear of coups that originated in the seventeenth century. Periodic crises, such as the Napoleonic Wars, would be met by the recruitment of volunteer units (yeomanry, fencibles etc) under gentry control - which produced its own problems in Ireland and America - culminating in Kitchener's Army.
In contrast, the Royal Navy grew proportionately in scale and importance with the expansion of empire, accounting for 60% of defence spending by 1912. The need to "patrol the seas", the frequency of small conflicts across the globe, and the lead times involved in commissioning capital ships meant a permanent commitment of funds that created its own institutional momentum (e.g. the way that naval estimates in parliamentary debate became excuses for jingoism). The modern-day "jobs argument" in respect of Barrow-in-Furness et al has a long pedigree, reflecting the extent to which the political management of the British military has predominantly been a matter of iron rather than blood, with the armaments industry having a significant influence on policy. Over the course of the twentieth century, the navy's role declined as the empire was dismantled, mirroring a parallel decline in the merchant marine and domestic shipbuilding. With the RAF taking on the main role in home defence, and the army maintaining its position through NATO deployments in Germany after WW2, the senior service might have expected to become the poor relation.
In the event, it secured control of our nuclear capability through the submarine fleet (the last airborne nuclear missiles were retired in 1998). This was not merely adroit inter-service manoeuvring, but a reflection of the elite preference for the nuclear deterrent to be independent of possible domestic interference, which could be better guaranteed at sea, particularly in a submarine cut off from the outside world for months at a time. In other words, the Radio 4 anecdote (that its absence from the airwaves would justify a nuclear strike), like the armed forces formal loyalty to the monarch, tells us that power ultimately lies beyond democratic control. For this reason, the question asked of Jeremy Corbyn is otiose: no British PM has ever had his or her finger exclusively on the button, so their ethical preferences are irrelevant. The decision to deploy a Trident missile would actually require the approval of both the US President and the UK Chief of the Defence Staff (who is appointed by the monarch); and if the PM refused a US request to fire British missiles, he or she could expect to be bypassed through an appeal to the head of state.
One of the chief arguments for retention of the bomb is that without it we couldn't justify our permanent seat on the UN Security Council, though it is obvious that what would really jeopardise our membership would not be unilateral nuclear disarmament but the insistence on pursuing an independent line from the US. Given the persistent (and growing) demands for the permanent membership to reflect current realities in terms of the possession of nuclear weapons (e.g. India) and geopolitical significance (e.g. Japan and Germany), we cannot assume that the UK will always have a seat, particularly if a Brexit left France as the default EU representative and expansion brought on more US allies. Even if we did retain a seat in an enlarged council, we might find ourselves marginalised: reduced to merely echoing the opinion of others and largely ignored (so no change there then). Trident represents a determination to keep us at the "top table", but largely to satisfy the egos of government and diplomatic elites, rather than to provide a lever for policy.
The media coverage of the military - from the sentimentality of sacrifice, through the nostalgia of cap-badges, to minor royals roleplaying Top-Gun - reflects an ambivalence over elite pretensions that can be traced all the way back to the seventeenth and early eighteenth centuries (i.e. the era of actual and potential military dictators, from Cromwell to Marlborough). On the one hand there's an admiration for near-feudal levels of fealty, dressed up in the romanticism by which Walter Scott subsequently recuperated rebellion as a conservative virtue; while on the other hand there is a suspicion of authority (assumed to be heartless) and a belief that the only soldier worth celebrating is a cripple (because both harmless and deserving). This ambivalence is often diverted into the trope of military madness, particularly in post-WW2 cinema (e.g. The Charge of the Light Brigade, The Bridge Over the River Kwai, Dr. Strangelove - the last as much a British as an American vision). In what other country would an anonymous general threatening a coup be laughed off as mere blimpishness? Indeed, in what other country would Colonel Blimp be an object of both derision and affection.
That Corbyn's honesty has been so quickly spun as evidence of his unfitness for office tells you much about the way that elite priorities have been internalised by the media. While overt threats of coups will be dismissed as infra dig - the sort of silliness that only hot-blooded Latin-types get up to - the reality is that Corbyn wouldn't be allowed anywhere near the "button", simply because there isn't one. The power of the deep state (i.e. those permanent interests in Whitehall and the military-industrial complex), and the power of the shallow state (i.e. those temporary interests in political parties and the media), depends not on the emperor's new clothes of the independent nuclear deterrent but on the belief in an emperor: the assumption that whether we do or don't have nuclear weapons we can still throw our weight around. The truth is that Britain only just managed to beat an incompetent Argentina in 1982 (a fight that we would almost certainly lose if it were re-run today) and since then have limited our military prowess to either playing Tonto to the US, as in Afghanistan and Iraq, or face-punching collapsing states, like Libya.
Ironically, in saying that he wouldn't press the button, Jeremy Corbyn is insisting on the independence of the UK's nuclear arsenal and thus the exclusive control of it by the head of a democratically elected government. That makes him potentially the most belligerent British Leader, from a transatlantic perspective, since Churchill in 1945. His statement is a clear signal to the US that a Corbyn-led government would pursue a more independent foreign policy, however we shouldn't automatically assume that this will cause furrowed brows in Washington. Given the gradual pivot in US focus away from Eurasia towards the Pacific, and the emergence of a Germany-dominated EU, this is something that future US administrations might well contemplate with equanimity, particularly if the membership of the Security Council is revised. The reality is that the UK's nuclear missiles neither significantly add to nor subtract from the global balance of power, and the US's future interests in Europe may be better served by a special relationship with Germany than with "Airstrip One". The threat that Corbyn poses to our elites is that he takes the myth of British military power seriously.