Is a second Scottish independence referendum inevitable, as Alex Salmond suggested at the weekend? Of course not.

What is inevitable is that at some point in the future, the SNP will include a commitment for a second referendum in its manifesto for a Scottish Parliament election. But the proportional election system used for Holyrood makes it murderously difficult for any single party to win an overall majority.

When the SNP managed to do it in 2011, it was considered a freak of nature and highly unlikely to ever be repeated. Remarkably, the feeling now is the party has a better than even chance of doing it again in May 2016, but that's only because it has been consistently north of 50% in all opinion polls published since the Westminster election.

No political force can possibly sustain that level of popularity indefinitely, but that's what would be required for the SNP to say to themselves "we can choose the optimum moment in 10, 15 or 20 years' time, and then go to the country again".

Even if they still find themselves in government by then, it's quite possible the Scottish Parliament will have reverted to the stable unionist majority that Labour always intended it to have.

Maybe the pro-independence Greens will change the equation by permanently replacing the Liberal Democrats as the fourth-largest party, thus making it easier for the SNP to put together a majority for a referendum when the time comes. But that's a "maybe" and falls a long way short of 'inevitability'.

The stars are aligned

Paradoxically, though, it's the very fact that a second referendum isn't inevitable that makes it more likely to happen in the relatively near future, perhaps within the next five years.

SNP strategists must know the stars are unlikely to ever be more perfectly aligned than they are right now, and that if they squander this opportunity they may spend the rest of their political lives bitterly regretting their caution.

Few people in the party thought in October 2014 that the possibility of another referendum would be under serious consideration so quickly but then again, nobody thought back then almost every Westminster seat in Scotland was on the brink of being seized.

The London government may be desperately trying to convince the world the most stunning election result in Scottish history has changed absolutely nothing, but it would be idiotic for the SNP to join in with that charade.

What we know is this. If the SNP decides to seek a mandate for a referendum in the 2016 election, it's likely – although not certain – they will secure it. That referendum campaign would be fought against combined unionist forces that are now vastly depleted.

Alex Salmond SNP
Alex Salmond said that a second referendum was \'inevitable\' on the BBC Sunday Mark Runnacles/Getty Images

Labour is no longer in any position to assume the leadership role as it did in 2014. The Yes campaign's chief would be the wildly popular Nicola Sturgeon, and its principal opponent would be a hated pro-austerity government, which received record low support in Scotland of just 14.9%.

It's likely that any attempt to recreate "The Vow" would be greeted with much greater scepticism by the public, who we know from polling evidence regard the current Scotland Bill as falling short of the grandiose promises made in September. And any repeat of the suggestion that opposing independence is all about "pooling and sharing resources" and maintaining a union of social justice will provoke only riotous laughter in the wake of the Tories' victory.

Perhaps the only piece missing from the jigsaw is a stable majority in the opinion polls for independence. No fewer than three polling firms (Survation, YouGov and Panelbase) have shown a Yes lead since the referendum, but all of them have shown narrow No leads as well.

There can be little doubt that the Yes vote has strengthened because it remains above 45% even after weighting by recalled referendum vote is applied. But the increase appears to be relatively modest.

The SNP will have to judge whether to treat that evidence in a glass-half-full or glass-half-empty sort of way. It may be emboldened by the fact that people who actually voted Yes seem for the most part to have remained rock solid in their support, rather than accepting the result and drifting away, as many would have expected them to do. That provides a formidable platform for a second Yes campaign to build upon.

David Cameron certainly seems to sense that an early referendum could on the cards, judging from his bizarre suggestion that he will personally overrule any mandate the Scottish people provide for one. It's difficult to know what he thinks he's up to.

The most logical conclusion is that he's trying to increase support in Scotland for a referendum, because that will plainly be the effect of any suggestions from London that Scotland's right to self-determination has been replaced with a hostage situation.

But as Cameron has nothing to gain from a referendum (assuming he's telling the truth about his passion for our "beloved United Kingdom"), it's perhaps more likely that he is catastrophically misjudging Scottish public opinion once again, and thinks the country is somehow receptive to colonial-style intimidation.

Catalan counterparts

He probably should have listened to his Scottish lieutenant, Ruth Davidson, who seems to have been begging him for months to accept Scotland's right to determine its only constitutional future. She even indicated during the election campaign that she had secured a commitment to that effect, leaving her now looking more than a little ridiculous.

The reality, though, is there is no legal consensus over whether Cameron even possesses the veto on a referendum that he would like us to believe he has.

Renowned Scottish legal expert Professor Robert Black left a comment on my blog a few months ago, setting out his view that the Scottish Parliament possesses the power to call a consultative referendum, within certain parameters.

That being the case, it's perfectly possible that Holyrood's presiding officer might certify a Referendum Bill as being within the parliament's remit, and then leave it for the courts to decide.

A London government being seen to use the courts to prevent the Scottish people deciding their own destiny would be the dream scenario for the pro-independence movement.

Ultimately, the electorate can't be stopped from having their say – the SNP would have the option of following the example of their Catalan counterparts by using an ordinary election to secure a mandate for independence. Or they could call a consultative referendum on maximum devolution, which everyone seems to agree would be within their powers, and ironically would be much easier to win.

One way or another, then, the game is afoot, and the prime minister's antics are only accelerating the process.

James Kelly is author of the Scottish pro-independence blog, SCOT goes POP! Voted one of the UK's top political bloggers, you can hear more from James on Twitter:@JamesKelly