ON the principle that even a mushroom cloud must have a silver lining, Labour’s Trident row has produced a warm, if not yet radioactive, glow. Should the worst come to the worst, it turns out, we will have the comfort of knowing that our end was a proper British farce.

A child of the 1960s and an adult in the 1980s, I thought I had all the facts where the nuclear apocalypse was concerned. I knew that a prime minister – a proper PM, not some peacenik surrender monkey – would give the order to launch the deterrent if, as it were, the deterrent had failed comprehensively to deter.

I also knew what’s supposed to happen if the UK ceases to be a “functioning state” and the PM is indisposed by virtue of having become a charred heap. In that event it will fall to the commander of the last Vanguard sub to proceed to the boat’s safe and take out a sealed letter. This document will contain the charred heap’s final orders for the non-deterring deterrent.

This much I had learned. Like most people, I had also presumed that Commander Swiftly-Doomed RN would do as he was told. Whether that would actually be the case is something we will truly never know. Until last week, though, there was another part that had puzzled me.

How would our heir to Nelson know to fetch the letter? If the UK is reduced to a non-functioning puddle of non-functioning people parts and melted mobiles, how would our Vanguard chap realise there was no longer much point in checking his Euromillions numbers, what with the sudden disappearance of Europe, far less reading a letter?

I found the answer towards the end of one among several hundred news stories on Corbyn the Wimp Defeatist. The plan is brilliant in a bonkers yet very British way. What would be the proof that existence had been terminated without so much as a replacement bus service? How would the Vanguard commander know to open the letter?

It would be “signalled”, said the news story, “when BBC Radio 4 can no longer be heard”.

Stands to reason, doesn’t it? There’s probably guidance in some extra-top-secret Navy manual. “When you can no longer hear John Humphrys shouting ‘Would you push the button? Would you? You know you want to’ at Jeremy Corbyn, the world has come to an end. Fire as many missiles as you fancy.”

It would make for a sombre moment. “That’s it, Number One. It’s all over. The Archers have bought it. Let’s give the filthy [please enter the name of a reviled foreign power here] rotters what for. This one’s for Queen, country and Ambridge!”

The chance to have The Archers wiped off the face of the earth is almost enough to turn me into a warmonger. It transpires, however, that when it comes to pushing the button, there’s a queue, with much of the Shadow Cabinet elbowing their way to the front. Last week, by all accounts, you could barely move in the wine bars of Brighton without being buttonholed by a senior Labour figure determined to declare a willingness to wipe us all out in the name of sensible politics.

It’s important to be clear about this. These people are not – I repeat not – threats to our national security. That’s Corbyn. An eagerness to declare yourself ready and willing to kill millions in the name of a patriotic soundbite is not the behaviour of a dangerous lunatic. That’s the traitorous Corbyn.

His declaration that under no circumstances will he order Commander Swiftly-Doomed et al to launch has forced – forced – these multilateralists to show their detestation for nuclear weapons by volunteering to fire a few. Soon they will demonstrate their absolute – absolute – commitment to non-proliferation and disarmament by ignoring their leader and voting to renew the Trident system. Cometh the hour, cometh the canting Shadow Cabinet nonentity.

In the words of Maria Eagle, Shadow Defence Secretary, Corbyn’s determination to stick by the principles of a lifetime and the promises he made before being elected leader by a landslide is not “helpful”. Ms Eagle’s opinion is very clear. Didn’t he read the advert before applying for the job? “Willingness to commit mass murder an advantage,” it said.

How did we get to this? Labour discarded unilateralism back in the 1980s. Its policy since has amounted to little more than quibbling with the Tories over the amount of potential thermonuclear carnage a budget can bear. But there has at least been a degree of decent inhibition over what total war means in the modern world. There has been a reluctance, at minimum, to talk about what the possession of nuclear weapons implies for a head of government.

Now the case is simple. Corbyn is damned as wrong because he would refuse to commit the final crime against humanity. If his colleague-critics are right, therefore, it means they would do the deed. In some cases, it sounds as if they would do it with a song in their hearts.

After all, in the psychotic logic embraced by Hilary Benn, Shadow Foreign Secretary and clearly a chip off the wrong old block, deterrence only works if an enemy believes you will use the weapon. Ergo, you must be prepared to use it. Hence the queue of volunteers.

Some of this is internal politics, Labour style. His Shadow Cabinet colleagues on the murderously sensible wing thought they had Corbyn encircled. Denied a conference debate over Trident, and therefore denied the chance of membership support, the leader seemed trapped by his own “collegiate” approach to disagreements. Defence policy seemed to be intact.

But if Corbyn becomes prime minister – the Shadow Cabinet’s alleged ambition – he alone will exercise the royal prerogative under which wars are launched. Only he will be able to give or refuse the order. To the amazement of a succession of BBC journalists who seem to think there must be a law against such temerity, he has chosen refusal.

Unlike certain of his colleagues, far less their Tory counterparts, Corbyn has an inkling of what nuclear war means. Seventy years after Hiroshima, understanding is elsewhere wearing thin. Memories are fading into black and white celluloid. The Cuban Missile Crisis is ancient history. First-hand knowledge even of the Cold War, of how close it came to superheated reality and how often, is becoming less common. You had to be around to remember the fear. In this, Corbyn’s age, at 66, is to his advantage.

Simple facts remain available, of course, for all ages. For all their defence-of-the-realm claptrap, Trident’s advocates cannot throw a flag over reality. Britain cannot afford weapons that it cannot, as even Tony Blair confessed, ever use. As Corbyn argues, meanwhile, the weapons do not keep us safe from the real threats we face. And they make the world far more dangerous than it ought to be.

“But deterrence works,” they cry. It is the argument of the junkie who never had a problem with those lovely drugs until, one day, the problem was defined as terminal.

Still: annihilate The Archers? Just how many silver linings could there be?