THE UK prides itself on having one of the most effective, far-reaching security and intelligence services in the world.

Between them, MI5 (the security service), MI6 (the secret intelligence service) and GCHQ (the Government listening and communications centre) aim to protect the country from terrorism, cyber-espionage and international organised crime. The agencies monitor instability in far-flung corners of the globe with a view to understanding the possible consequences for the UK and ensuring our interests are safeguarded.

They work in long-established alliances with the US, Canada, Australia and New Zealand (the "Five Eyes" pact) and the Club of Berne, the information-sharing agreement among European nations. The cost of this largely invisible safety net runs into billions of pounds a year.

In its blueprint for independence, the SNP proposes to emulate the existing arrangements. A £200 million a year Scottish Security and Intelligence Agency would be created to protect the country "from day one of independence," according to the SNP's White Paper, Scotland's Future. It would work hand in glove with allies south of the Border. Information would be shared much as today. The proposal is designed to reassure but, according to the Royal United Services Institute (RUSI), they are unrealistic and unaffordable. A briefing from the respected defence think tank finds the White Paper's vision highly unfeasible. Interestingly, though, it also finds it largely unnecessary.

First, the unfeasible. RUSI questioned almost every aspect of the SNP's plan, suggesting the failure to consider the high start-up costs was a fundamental flaw and warning, regardless of existing arrangments, that an independent Scotland could not expect to share the UK's secret intelligence. It said that, even in Nato, an independent Scotland's potential anti-nuclear policy would create tensions with the UK and other allies.

Indeed, the report suggests the UK's main motive for co-operating at any level would be the fear an independent Scotland would become a weak link: "an attractive environment for hostile intelligence organisations" and a good base from which to spy on the rest of Britain.

As a demolition of SNP policy, the RUSI report could not be more devastating. Yet there will be just as many people in the broader independence movement as in the pro-UK camp who welcome the findings. "An independent Scotland is unlikely to face the severity of threats currently faced by the UK," conclude the RUSI analysts. "Given this more benign threat picture, the creation of a new Scottish Security and Intelligence Agency seems unnecessary."

In other words, when it comes to fighting existential threats, an independent Scotland need not worry too much about keeping up with the Joneses down south. As such the report raises deep questions about Scotland's place in the world, how that might change under independence and whether people would welcome a redefined role. A wider discussion of those issues would be welcome in the independence debate.