John Swinney is already promising a 'prize' for SNP voters that he has no way of delivering

A majority for the SNP in May’s Holyrood election will, says John Swinney, force the UK Government to green-light a second independence referendum. This is the “prize” within nationalists’ reach.

For weeks now, Swinney has been promoting the idea that a fifth consecutive Holyrood victory for the nationalists will trigger another constitutional battle. His case is simple and straightforward: After the SNP won an overall majority in the 2011 Scottish Parliamentary election, then Prime Minister David Cameron felt compelled to agree to a referendum on independence. Should the nationalists’ achieve a similar result this year, the current (at time of writing) inhabitant of 10 Downing Street, Sir Keir Starmer, would have no choice but to do the same.

There’s a simple logic to Swinney’s argument but, I’m afraid, it assumes a lot.

There are a number of reasons why victory for the SNP next month will not see Starmer commence talks on Indyref2.

First, foremost and, surely, most frustrating for the nationalists is the fact that neither Starmer nor any other Prime Minister of the United Kingdom would, on the current numbers, fancy the gamble of another vote on the constitution.

When David Cameron agreed that 2014’s referendum should proceed, support for Scottish independence sat at less than a third. Given this starting point, the then PM believed – not unreasonably – the risk of defeat was slender.

David Cameron shook Alex Salmond’s hand over the 2014 referendum because he was certain the nationalists would lose. But current polls show Scots now more evenly divided on the constitutional question. If the Yes campaign could swing the dial from 27 to 45 per cent during the first referendum campaign, where could it take its current 48 per cent during a second?

SNP taunts that Labour is running scared of another referendum are perfectly accurate.

Beyond uncertainty over the result, no Prime Minister, either Labour or Conservative, could currently sell to the rest of the UK the idea that, yet again, the national debate should be focused on Scotland’s place within it. Voters in England, particularly, would not, I think, welcome months of interventions from whingeing Jocks.

Haven’t they already had their referendum?

Current polling has the SNP falling short of an overall majority in May but a decent night for the Scottish Greens could easily see pro-independence MSPs form the dominant bloc in the next parliamentary session.

Green co-leaders Ross Greer and Gillian Mackay already enjoy convivial relationships with Swinney. Although a repeat of the past formal coalition between the SNP and the Greens is unlikely, we can expect the parties to work closely and to be firmly united in demanding the UK Government agrees to another referendum.

When this is refused, the grind will continue. We will hear of democracy denied, of Scotland betrayed. On and on it will go.

Back in 2014, as they sought to bring home of the urgency of the occasion, Alex Salmond and Nicola Sturgeon described the independence referendum as a "once in a generation” event. On occasion, it was “once in a lifetime”.

It took barely two years before the SNP was demanding Indyref2. Defeat for the Remain campaign in the EU referendum had produced the material change in circumstances required for another vote on Scotland’s place in the UK to be necessary.

During eight and a half years as First Minister, Nicola Sturgeon repeatedly promised her supporters a referendum she had no power to deliver. As her time in power drew to a close, her twin obsessions of independence and trans rights had overshadowed everything else she was supposed to have been in office to achieve. The wider policy agenda was neglected as Sturgeon focused on engineering a referendum that was never going to happen.

It is easy to understand why this happened. The dial had shifted considerably towards independence during the referendum campaign and polls showed support continuing, slowly, to grow. That Sturgeon’s instinct was to keep pushing was hardly a surprise.

But, for all her efforts, support for independence has not advanced far enough. At the same time, an unfocused Scottish Government has failed to tackle falling standards in schools or a growing crisis in the NHS.

Some veteran SNP figures privately talk of the need to “park” the independence question if their cause is to progress.

One former member of the Scottish Government says that support for independence grew under the First Ministership of Alex Salmond because his government of 2007-11 had, across the policy agenda, actually done the sort of things people expect of a government. This is no longer so.

The SNP should, says this former minister, declare that, while independence remains its aim, it will not seek a referendum for the next parliamentary term.

“They should propose something along the lines of they invite the UK Government to engage with them on a future agreement and then get on with some proper policy stuff on education and health. If they make changes there, then the independence dial will move. That’s when you come back to it.”

Another former senior SNP politician recently suggested to me that, if their party falls short of a majority in May, it should seek an agreement to govern with Labour, with the price of a deal being the withdrawal of opposition to a second referendum “perhaps after a period of five years”.

I think that scenario, intriguing though it is, highly improbable.

Instead, I expect a victorious SNP to demand, with increasing urgency, another vote on Scotland’s place within the UK and for the neglect of public services to continue.

It is this monomania that will keep Indyref2 perpetually within sight but out of reach.