Nineteen years ago, Michael Forsyth said the creation of an Edinburgh parliament with tax-raising powers would lead to a "jobs holocaust" in Scotland. It was a classic piece of Tory hyperbole. In the run up to the 1997 referendum, the Conservative Party used every scare tactic, no matter how ridiculous, to push for a No vote. At one stage, Michael Ancram, its constitutional affairs spokesman, even appeared to compare devolution to fascism: "Like Churchill before the last war, we see the terrible dangers ahead and we give warning".

The Tories weren’t alone in issuing silly threats against home rule. Sir Alastair Grant, of Scottish and Newcastle breweries, argued that anything other than a fiscally toothless parliament would make the Scottish economy "significantly uncompetitive", while CBI Scotland howled about the dangers of "tartan taxes". Indeed, Scottish business as a whole seemed hostile to change. Not long before the vote, a poll for the Scotland on Sunday suggested 76 per cent of Scottish companies opposed devolution.

What was it Marx said about history, tragedy and farce? One month ago, Ben van Beurden, the chief executive of oil giant Shell, told his shareholders that he "valued the continuity and stability of the UK" and therefore wanted Scotland to remain in the Union. Van Beurden’s remarks came just a week or so after BP boss Bob Dudley said he thought "Great Britain should stay great", and only a few days after Standard Life and RBS revealed plans to move south if Scotland loses the pound after a Yes vote. Since then, Alliance Trust, Barclays and Aggreko have made similar noises.

To some extent, these interventions do little more than confirm a general – and fairly obvious – rule: business doesn’t like uncertainty. British companies are almost as uneasy about the prospect of the UK leaving the EU as they seem to be about Scotland leaving the UK. In 2013, the British Chambers of Commerce polled nearly 4,000 firms and found that more than 60 per cent of them wanted the UK to stay part of Europe (albeit with a renegotiated settlement). Ford, Renault and Unilever have all said they intend to scale back their British operations following any rupture with Brussels. This isn’t a comment on the merits of the European project. It’s simply a reaction to the threat of disruption.

However, the interventions also tell us something specific about nationalist strategy. The SNP’s "prawn cocktail offensive" – its ongoing attempt, since the early noughties, to persuade Scottish business figures that they have nothing to fear from the party or its overarching goal – isn’t working. For the last decade, the SNP has gone out of its way to coddle and reassure Scottish capital. It has promised to maintain the current system of UK-wide financial regulation. It has aggressively pursued a currency union. It has opposed a financial transactions tax at the European level. It has courted zero-hours employers such as Amazon. Bafflingly, it has even pledged to undercut the UK corporate tax rate by 3 per cent. And yet Scottish business (most of it anyway) remains pretty much wedded to the British state.

I expect the SNP’s efforts to "de-risk" independence to unravel further as the referendum approaches. Despite one unnamed UK minister raising the prospect of a deal over monetary union, Alex Salmond will struggle to hold the line on the currency for another five months. At some stage, he will have to lay out some sort of back-up plan in the event post-Yes talks fail to secure a formal "sterling zone" agreement. (The Fiscal Commission is already taking a "second look" at the alternatives.) Nor can the SNP go on blithely asserting that an independent Scotland will assume its EU membership under precisely the same conditions it enjoys as part of the UK. Those conditions will be up for negotiation after a Yes vote.

But here’s the interesting thing: there’s no reason to believe any of this is going to damage the Yes campaign. Since the start of the year, Better Together has thrown everything at the nationalists, from Osborne’s belligerent currency rhetoric to repeated threats of capital flight to umpteen apocalyptic predictions about shipyard closures – and support for independence has steadily increased. My guess is that this trend is due to growing numbers of low-income Scots shifting from No and Undecided to Yes. These voters don’t benefit from the status quo. They don’t want to hear that an independent Scotland will look exactly the same as the current, unionist one. The more radical the Yes campaign’s message becomes, the more likely they are to turn out in force on 18 September. With the momentum shifting slowly but surely in favour of Yes, the SNP and its allies have no excuse for playing it safe anymore.