THERE are some ideas that, no matter how daft they are, never seem to go away. And so it was this week as the idea that the SNP’s decades-long commitment to ridding Scotland of nuclear weapons after independence would be sacrificed in favour of a long-term leaseback agreement surfaced menacingly like a Vanguard-class ballistic missile submarine in the Firth of Clyde.

While opponents of the SNP on the left and Unionist right love to latch on to this idea – put forward by defence wonk Stuart Crawford – it is an idea which swiftly dives to depth again when confronted with one salient point: that in the 75-odd-year history of nuclear weapons, no state has chosen to site the entirety of its nuclear deterrent in an area completely surrounded and secured by the sovereign territory of another state, even a friendly one. After all, the calculations that led to the UK Government basing the continuous atsea deterrent at HMNB Clyde in the 1960s – a decision motivated in no small part by the considerations of American allies from whom it wanted to purchase the Polaris system – will have entirely changed.

Faslane drew the short straw then, many experts agree, because it was close to a major conurbation, deemed vital for sailors coming ashore after months on patrol under the cold waters of the North Atlantic.

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It was a decision made despite the significant weaknesses of the location: leaving the Gare Loch, UK subs must pass through a serious of narrow “choke points” such as those between Rosneath and Rhu; Gourock and Kilcreggan; and Bute and Little Cumbrae, which makes to base particularly vulnerable to interference in times of peace and in war.

It was a point first made to me by SNP member and former RAF Cold War sub-hunter Geoff Tompson. There was a range of options for a potential enemy, from relatively low-impact observation of subs’ movements in the vicinity, to the improbable – yet devastating – potential of a vessel being scuttled close to the narrow entrance to the Gare Loch, completely dislocating the entire UK nuclear deterrent.

These risks, serious enough when the UK completely controls most of the variables, become insurmountable in the event of Scottish independence and make a precipitous exit entirely in its interest. And this is before we even begin to consider the obstacles the rUK would face in moving Trident nuclear warheads around. Currently – as well documented through the excellent work of Scottish CND – dark green lorries trundle ominously between Faslane and the Atomic Weapons Establishment at Aldermaston in Berkshire, laden with enough material to destroy cities and murder millions.

How would the rUK realistically hope to continue this practice when the last couple of hundred kilometres of that journey were no longer through its own sovereign territory? If you hope – as I do – that a commitment to a nuclear-weapons-free Scotland would be enshrined in our constitution, how would governments local and national square that ironclad commitment to the Scottish people with the regular appearance of weapons of mass destruction on the M74?

As the MP for West Dunbartonshire, I certainly couldn’t look my constituents in the eye if they continued to pass through my constituency long after independence. The “Faslane leaseback” option has been around for quite a while: most prominently put forward in Malcolm Chalmers and Professor William Walker’s 2001 book Uncharted Waters: The UK, Nuclear Weapons and the Scottish Question and since by a range of figures, most recently an SNP CND paper – covered in The National – that went as far to say some in the SNP were attracted by the idea.

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Now, SNP CND’s arguments didn’t deal with these logistical issues, and seem to focus mainly on the financial imperative which an independent Scottish government might be faced with when considering the future of Faslane: namely that the rent they could charge to keep Trident away from England’s green and pleasant land could provide an incentive for the SNP to be more malleable with what had previously been an ironclad commitment.

Sadly, I think this argument doesn’t stand up too well to scrutiny either. Any rent charged would have to be considerable in order to compensate for the loss of a purpose-built base for the tri-service headquarters of Scotland’s own armed forces. Faslane and its vicinity is the future site of barracks for soldiers of the Scottish Army; deep-water berths for ships of the Scottish Navy; training grounds for amphibious operations of our future Special Forces – all of which would have to be built elsewhere at great cost to the Scottish exchequer, and potentially further away from our largest population centre. How can you put a price on that?

AS a member of our Westminster defence team since I was elected in 2015, I can say it has never something that has been advocated by anyone looking out primarily for our future defence and security prospects, and ability to contribute to the safety of our wider neighbourhood – you can’t put a price on a consistent geopolitical strategy.

It is an policy that is superficially attractive, primarily to those outside of the SNP, either as an economic quick fix, or as a way to attack the party from the left, to make it seem like we are going soft on what is ultimately a matter of faith for every SNP member.

When I spoke to the SNP CND group last month, I made it clear it is my opinion that the current SNP position – the removal of Trident nuclear weapons from the Clyde as soon as possible after independence – does not need updating. Our political will is unshakable.

What is less well-known are the technical aspects which will determine the speed of that withdrawal, and it is unlikely that the UK Government is going to let these be discussed in public without anyone breaching the Official Secrets Act. That said, from discussions with those in the know, in Scotland and elsewhere, I’ve had no reason to doubt that the two-year time frame discussed in the much-missed John Ainslie’s Disarming Trident report from 2014 is a useful starting point.

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So while Stuart Crawford’s contribution to the debate about defence and security in an independent Scotland should be welcomed, it’s not something I think the SNP will ever be able to get on board with. As my friend and SNP defence spokesperson Stewart McDonald said, “most Scots would find it unacceptable to have achieved their independence only to try to secure that independence on the cheap”, and we owe it to Scottish voters to demonstrate that we have a comprehensive and sovereign security plan.

Indeed, such an “Ireland-style” arrangement, whereby an independent Scotland was reliant on the UK and other allies to undertake some of the most basic tasks protecting our aerial and maritime sovereignty is not on the cards. As on other matters, it is our Nordic neighbours who should inform our thinking when it comes to securing independence.

So, as ever on issues of national security, I’ll remember what my granny used to say: if you buy cheap – you buy twice!