The lies of our own dear leader are easily exploded

The bracing threat of the juvenile dictator's puissance has caused the Prime Minister to misspeak, however. Or rather, to misspeak a little more than usual. After talking to workers at Thales in Govan on Thursday, Mr Cameron described the grim danger posed by Kim.

Our own dear leader said: "The fact is... North Korea does now have missile technology that is able to reach, as they put it, the whole of the United States and if they're able to reach the whole of the United States they can reach Europe too. They can reach us too, so that is a real concern."

Mr Cameron didn't say whether Kim could launch in 45 minutes, or whether there was a Downing Street dossier to prove it. A quick check of the prime ministerial "fact" established that the disco-dancing tyrant's biggest rocket, the Taepodong, has a maximum range of 6000 kilometres. London is 8657 kilometres from Pyongyang. The remote, notional threat is to Guam, not Govan.

You could laugh it off as typical of the cavalier Mr Cameron. The problem with that is two, three and even fourfold. First, the Prime Minister must really think we are stupid. Second, he was using his "fact", his serious face and insane rhetoric from the other side of the world to justify a £40 billion Trident renewal programme.

Third, Mr Cameron was casting aside a solemn promise, part of the coalition agreement, to review the weapons system, like-for-like replacement and a "continuous at-sea" deterrent. The study is in the charge of Danny Alexander, Liberal Democrat best boy at the Treasury, and is not due to report until June. Mr Cameron, having already committed billions to "preparatory" work for a new Trident, simply said it would be foolish not to proceed.

Fourth and last, the Prime Minister was using a fib about Kim's missiles to scare up a threat to Scotland's defence and to Scottish jobs. North Korea was proof, in Mr Cameron's telling, of the need for a nuclear deterrent. The British deterrent was in turn the best guarantor of defence jobs and defence security for Scotland.

Back in the Cold War, a lot of people consented to nukes because the underlying proposition seemed, however illogically, to have merit. Knowing the likely cost, America and the Soviet Union were deterred from a definitive fireworks display. Unilateral disarmament was "going naked into the conference chamber", as Nye Bevan had claimed. It left a peaceable nation without bargaining chips.

How does any of that apply to North Korea? The chubby princeling of Pyongyang is threatening a pre-emptive strike, not quaking in his designer shoes (publicly, at any rate) at the thought of a response. He has not been deterred in the slightest from listing the places he wants to immolate.

And where has negotiating from nuclear-armed strength got us in terms of disarmament and non-proliferation? South Africa has been the single success. Other nations with enemies, real or imagined, have looked at the big boys and demanded their status symbols. Non-proliferation is the deceit that has allowed Israel, Pakistan, India and North Korea to join the club, with Iran knocking at the door.

Still, as Mr Cameron was keen to tell Thales workers, all of this is good for Scotland. He said: "There are more than 12,000 people employed in Scotland in defence industries – defence industries that are backed by the whole of the United Kingdom with a defence budget that is the fourth largest in the world."

This time he had his facts more or less in order, but those facts are not quite what they seem. It is true that Britain is fourth largest in terms of global total military expenditure, but Mr Cameron shouldn't get too carried away. The British share of the total is 3.8%, that of the United States 43%.

We only make the list, in any case, because of governments prepared to spend £40 billion on a weapons system whose key elements remain under American ownership and control. Meanwhile, ordinary service personnel are laid off or starved of equipment. A great many more than 12,000 jobs could be created, you might think, with that £40 billion.

Still, it remains a lot of jobs, jobs we can ill afford to lose. Mr Cameron, who otherwise pours contempt on the dependency culture, is inviting us to stay dependent and be grateful for it. Grateful enough, at least, to give a vote of thanks in the independence referendum.

While in Govan, though, he let slip an acknowledgement of what gratitude might be worth. Defence, he admitted, "can't be exempt altogether from difficult decisions". In other words, there will be more cuts after 2015 thanks to George Osborne's spending review. For solace, the Prime Minister added: "Within that we've said that we need to protect the equipment budget and we do need to make sure that equipment budget is properly funded..."

Here's a few facts I didn't invent. According to the Aerospace, Defence and Security (ADS) trade association, defence supports 300,000 jobs in Britain. Ministry of Defence equipment spending accounts for 75,000 of those jobs. There are 22,000 posts in the English south-east, 19,000 in the south-west, 12,000 in the north-west. There are perhaps 4000 in Scotland.

The Prospect union is up in arms, so to speak, over the effects of defence cuts on the private sector. But Scotland is already doing badly on that score as part of the British partnership, certainly terms of a population share. MoD employment here fell by 900 jobs last year, the armed forces, prior to the most recent cuts, by 700.

The bigger picture, when the SNP managed to gouge the numbers out of Whitehall, is not pretty for anyone joining Mr Cameron to extol the benefits of Union in terms of defence. Of £60 billion spent between 2007-2008 and 2011-2012, £3.17 billion came Scotland's way. That was getting on for £2 billion less than should have been spent if population was a guide. We will, however, fork over our per capita share of the £40 billion Trident nonsense.

Labour, heading for a pre-coalition tryst with the Lib Dems over bargain nukes, is another party that presents weapons of mass destruction in terms of job security. Their line is that 11,000 jobs depend on Trident and the Clyde naval base. The number employed is 6500, but it's another big number. A Freedom of Information request from Scottish CND has established, however, that only 520 direct civilian jobs are at stake.

Even that, too, is a lot of jobs. It is difficult to believe, as the SNP knows too well, that an independent Scotland would replace every post associated with Trident. On the other hand, a non-nuclear country would be spending far less than its present share of the defence bill and be spared the vast future cost, financial and moral, of weapons of mass destruction.

It would also be defended against the risk of having its intelligence insulted by a Prime Minister running short on facts and bogeymen. Intelligence is worth something when you come to cast a ballot.