If the SNP win a majority at next year’s Holyrood elections, the UK government should be prepared to start independence negotiations with them. This may sound like a mad idea, at first. But as I say in the magazine this week, it might actually offer a way to save the Union.

Rather than saying a straight no to another independence referendum, the UK government would tell Nicola Sturgeon she could have one, if the terms of independence were negotiated first. This would take time – unravelling a 300-year-old political, economic and military union would make Brexit look like child’s play – but it would mean that when the referendum came, it would be on the realities of independence not just the idea of it. This would give the Unionist side a far better chance of winning it. It would force the Nationalists to answer questions they would rather avoid: what currency an independent Scotland would use, what share of the UK national debt it would take on and more. We’d see what the border arrangements between this new state and rUK (the shorthand for the rest of the UK) would be, and how trade would be managed with the two countries in different customs unions.

This approach might lead floating voters to conclude that the status quo is better than the proposed alternative. Remember that ahead of the referendum on the monarchy in Australia in 1999, most voters were in favour of the country becoming a republic. But the actual option on the referendum ballot paper that year could not command majority support. It might also bring out the fissures within the Nationalist movement. Ahead of the EU referendum, Dominic Cummings was clear that the Leave campaign shouldn’t embrace a specific version of Brexit because it risked fracturing its own coalition. The same logic applies to Scottish nationalism today.

Number 10’s current view is to just say no to any SNP demand for another referendum. No legal referendum can take place without Westminster’s consent, and they can’t lose a referendum they don’t allow. But as those who think deeply about this issue in government are beginning to conclude, this strategy might not be sustainable.

The danger is that every time Sturgeon’s request is knocked back, support for independence goes up a point or two until it breaks sixty per cent and it starts to feel like any referendum would be a confirmatory exercise. To save the Union, the government might have to negotiate independence.