DEFENCE of the realm. As I write, it’s today’s hot topic on the Generation Game conveyer belt that is the run-up to next month’s election.

Besides being the only time the word ‘realm’ is ever used and making senior politicians sound like they’re auditioning for a part on Game of Thrones, it may well prove to be a pivotal issue this time round – before and after polling day.

While you read this, a nuclear armed submarine is roaming the seas like a crazed Poseidon, armed to the teeth with warheads off the coast of, say, Cleethorpes, in a bid to keep us safe.

But with the UK’s four Vanguard nuclear subs reaching the end of their useful life, the question of whether to Trident or not to Trident is the policy of the hour.

With a conservative (with a small ‘c’) estimate of £25bn to renew the Trident project, the now-relevant Scottish Nationalists are pledging to scrap the lot.

And with a hung Parliament a near certainty, both Labour and the Tories are understandably prepared to turn their doe-eyed gaze to anyone to break the deadlock.

But the steely Nicola Sturgeon is sticking to her guns on this one – pun intended – and has drawn an imaginary non-negotiable red line under Trident.

This red line may very well have been a blue line, if the Tories were willing to talk about the options over the nuclear deterrent.

But David Cameron is absolutely adamant, and keeping Trident is one of the very few things he seems to muster any real enthusiasm about these days.

So that leaves Labour, who the PM has already accused of plotting to do a deal over scaling back Trident. And who could blame them? Given the number of seats the SNP could garner north of the border (ironically many of them Labour seats), they may need all the help they can get.

Sturgeon’s red line may also end up tracing Hadrian’s Wall if the SNP’s bargaining power with Labour were to increase.

While unlikely, the feisty Scot is now talking about full fiscal autonomy north of the border – or “devo-max” as the political hipsters say.

This dreamy, halcyon scenario would see Scotland hold its own purse strings in most areas – but not defence.

Instead that’s left to Westminster to salami slice, with the chunks lopped off the military sausage likely to be larger than before.

It just doesn’t seem fashionable to throw money at our lads in the armed forces right now, with the Tories unwilling to pledge the two per cent of GDP as recommended by NATO.

And Labour have suggested shedding army top brass and say they will carry out a “strategic defence spending review” – and we all know which way the cashflow graph goes after one of those.

Only UKIP have vowed to hold spending on the military, with pictures of Nigel Farage standing on a tank likely to bring a nationalistic tear to the eye of the sort of voter who likes to see Nigel Farage on a tank.

Whether it is wise for a party seen by some as xenophobic to cut foreign aid spending and bolster our gun cabinet is up for debate.

And with Trident and the armed forces becoming a political football again, my own views on Trident are locked in a midfield stalemate.

I can see that anything up to £40bn for a system we will in all probability never use could be put to a hundred better uses. But rickety old submarines wobbling around the Channel with nuclear explosives while I’m enjoying a day by the seaside? I’m not so sure about that.