The AUKUS submarine deal between Britain, the US and Australia has cast an unflattering light on the Scottish National Party’s Cold War-style fixation with getting rid of the Trident submarine base at Faslane on the Clyde. This is important politically because being ‘anti-Trident’ is one of the few remaining policies that the SNP espouses which is genuinely popular with voters. Take that away and the party’s support base would shrink dramatically.

Now that Brexit is no longer available as a Scottish spanner to throw in the UK works, it is remarkable how many previously popular policies have also fallen by the wayside. Nationalisation once raised a big cheer, but that has been dying for decades. The health service has been put in a position where the government looks more hostile to it than helpful. The Hate Crime Bill is increasingly seen as an oppressive rather than a liberating measure, and ideas like a national energy company and a government investment bank appear to have been abandoned completely. Land reform was once popular, but was ditched when the SNP’s strategists came to realise that young people with smartphones do not tramp the hills.

That leaves the SNP with little more than hating Tories (of course), promoting special-interest group policies and moralising about a nuclear submarine base.

Of these, the Tories will be a permanent fixture so long as they are in government, and special interests of one kind or another ‘ye have always with you’. Neither can be influenced much either by SNP behaviour or by London. But Trident is altogether different. This is the ‘swing’ policy. It is a genuine bone of contention.

If Sturgeon chooses to emphasise it, as happened for a few weeks recently before the party Conference, she can make serious trouble for Downing Street’s precarious authority in Scotland. It is the one issue of genuine principle which has survived Ms Sturgeon’s post-referendum encounter with the slings and arrows of actual, day-to-day government – ‘events, dear girl, events’. The Government in Westminster must not ignore it.

So what is the main argument that might be put to the Scottish electorate to persuade it to put up with nuclear submarines on the Clyde in the light of the AUKUS deal? Essentially, it is similar to the one which appears to have swayed the Australian government when faced with a rising China and a declining confidence in the effectiveness of pre-nuclear technology. Australia has come to realise that it will soon be in the front line in the fight against an expanding China which is aggressively opposed to the rule of law. It needs a proper, nuclear-powered defence capability. But how does that apply to Scotland?

The simple answer is the Arctic sea route, which will soon be bringing China much closer to Muckle Flugga. As the sea-ice continues to melt, and Russia builds more (nuclear-powered) ice-breakers, it will become easier and cheaper to connect China with Europe. Even from Shanghai, the ‘over the top’ journey to Rotterdam is about a third shorter than through the Malacca Strait and the Suez Canal. Most of it is guarded by a friendly power – Russia – and it skirts no war zones or piracy hotspots.

I was recently involved in production of a report on these matters for the main Russian think-tank, the Skolkovo Management School in Moscow. It reported forecasts that up to 1% of all the world’s sea-borne commerce might one day be plying this route. It also noted the determined push China is making to join the Arctic Council (formed in 1996). In 2016 China established its first overseas satellite receiving station, in the Swedish town of Kiruna. This was connected with the launch, in 2019, of a micro satellite to track ice drifts and iceberg thaw rates in the Arctic. China is clearly planning to make use of this route through to the Atlantic. That is where Scotland comes in.

Scotland’s geographical position makes it the gate-keeper for Europe of the Arctic sea route. It lies at the hinge of the Arctic and the Atlantic. If an independent Scotland went broke, which is quite likely, it would be vulnerable to the Chinese Belt-and-Road initiative. It would find it hard to resist tempting offers of finance in return for port concessions – perhaps at Faslane itself. What if China ‘bought’ the Gare Loch from Ms Sturgeon, rather in the way that it has established itself, with extra-territorial rights, at Gwadar port in Pakistan? Or it might also fancy Scapa Flow, or Campbeltown to control the North Channel. What would ‘a free Scotland’ look like in that context?

The best way for the Government in London to attack the SNP’s anti-Faslane policy would be to tell the truth and portray the Scottish government as fighting the next war with the outlook and methods of the last one. The Cold War ended 30 years ago and the idea that bobble-hatted sit-downs and rain-sodden Peace Camps will be noticed in Beijing is dangerous, naïve nonsense – ask the Uighurs.

That is why it is so important to convince anti-nuclear Scots that if they want to ensure a continuous supply of cheap badminton racquets and suspiciously capable mobile phones, there are only two long-term approaches: keep the Chinese out and respectful by staying in the Union or sell them Faslane and watch Beijing turn the Hebrides into the South China Sea. In either case, there will still be nuclear weapons in this neck of the woods.

Better to stick with the devil you know.

Click here to subscribe to our daily briefing – the best pieces from CapX and across the web.

CapX depends on the generosity of its readers. If you value what we do, please consider making a donation.