LAST week I wrote about why there is next to no reason Boris Johnson would grant an independence referendum.

Life as a Prime Minister is nasty, brutish and short enough as it is without Indyref2 as a headstone.

Mr Johnson will play for time, shuffle and shrug, hope something shows up, and generally try to skulk away from the march of history.

He may be a particularly self-interested, short-term sort of Prime Minister, but the same logic will appeal to the next occupant of Number 10 and the one after that and so on.

No politician strives for years to secure the top job only to take on a referendum that might end it in a few traumatic and humiliating months.

David Cameron didn’t think he’d win a majority in 2015 and have to deliver a Brexit vote, and then didn’t think he’d lose it anyway.

Both Prime Ministers since and all would-be PMs polishing their blades in the wings have learned the lesson. Referendums can kill. Do not touch.

Which might sound like a counsel of despair for the Yes movement. It’s all hopeless, everybody down flags.

Well, no. I think a referendum is a distinct possibility. But not on any timescale mooted by the SNP.

Consider what the party’s Holyrood manifesto in 2016 said about the issue.

At that point, the EU referendum was nigh, but the general assumption was that Remain would win.

“We believe that the Scottish Parliament should have the right to hold another referendum if there is clear and sustained evidence that independence has become the preferred option of a majority of the Scottish people - or if there is a significant and material change in the circumstances that prevailed in 2014, such as Scotland being taken out of the EU against our will,” said the SNP.

The second part is usually quoted, but it’s not the most interesting bit.

A significant and material change in the circumstances that prevailed in 2014? Well, duh. That’s called life. Politics moves on, the world moves on.

The year 2014 was never going to be trapped in a time capsule, pristine and immutable. Of course something was going to come along. Change happens.

As it turned out, much to the SNP’s surprise, there was a vote for Brexit.

But if the SNP had delivered their 2019 general election pledge to “stop Brexit”, a near-Brexit would still have been touted as a reason enough.

Or if Brexit had been rejected in 2016, it would be the pandemic and its economic calamity that would - perfectly reasonably - be cited as a big material change since 2014.

Indeed, John Swinney this week said it made independence an “essential priority” for the recovery.

But if Covid hadn’t come along, 2014 would still be a different country, slipping hazily into the past.

So the “significant and material change” clause isn’t a great persuader.

Demanding a rerun on the basis of something inevitable, while claiming it’s a big surprise, isn’t going to cut it.

It’s a heads-I-win, tails-you-lose sort of argument. Cute, but see-through.

But the first part of that manifesto section is very different. This is where the SNP was onto something.

There is nothing inevitable about independence becoming the clear and sustained preference of most Scots.

That is a specific shift, not a nebulous formula, and it has the potential to deliver a referendum not because it was in an SNP manifesto, but because it offers a British Prime Minister an escape route.

At the moment, the UK Government’s take on Indyref2 is, You can’t lose if you don’t play.

But there’s another way not to lose. You can’t lose if you can’t win. You can’t lose if there’s no contest. You can’t lose if it’s a foregone conclusion.

Take the 1997 referendum on devolution. Decades in the making, the landslide result was always in the bag.

The new Tory party leader, William Hague, campaigned against it, but there was no question of him resigning when the results came in. He lasted four more years in the job.

While another No campaigner, Brian Monteith, became a Tory MSP in the parliament he opposed barely 18 months later. Voters and political colleagues can be rather forgiving when it comes to lost causes.

The reason Indyref2 is off the cards at the moment is because the outcome is uncertain. It would be a real contest.

Any Prime Minister would be obliged to fight for their political life.

If the result went against them, they would be judged to have lost where a better, more credible campaigner could have won. They'd be out.

But if support for independence had long been the clear and sustained preference of the Scottish people, those judgments would not apply and nor would the consequences.

If the result had been obvious to the rest of the UK, and to English voters in particular, a British Prime Minister could survive a vote for independence.

Naturally, they would sigh and mourn the passing of the Union, but their career need not die with it.

For years, the SNP has been told what it needs to do is reach out to No voters to win the next referendum.

But just as significant are those who didn't have vote in 2014 - the English.

Convince them independence is surely coming, that it’s not personal just the juggernaut of history, and their MPs can start to contemplate it too.

When most of Westminster is, if not happy, but reconciled to a defeat, granting Indyref2 becomes possible.

You can't lose if you can't win.

It may be a fair wait. But no PM, not just this one, is about to grant a referendum until they feel the fallout from losing is manageable for them, their party and what is left of the UK.