IF the latest poll from Find Out Now is correct that the SNP are on course to retain 40 seats at the UK General Election, it would arguably be the greatest achievement in the party's history.

Although it would fall short of the 56 seats won in 2015 or the 48 seats won in 2019, it would be a landslide triumph secured in infinitely more challenging circumstances - without the stardust of Nicola Sturgeon's leadership and without the assistance of Labour looking like no-hopers.

Indeed, the poll suggests Labour would win the vast majority of seats in England to claim a victory of utterly unprecedented proportions, meaning the SNP would have succeeded in bucking a seemingly unstoppable Britain-wide trend.

Humza Yousaf's troops would still control more than two-thirds of Scottish seats at Westminster, a proportion roughly on a par with what Labour secured across the UK in 1997 and 2001 – when Tony Blair was at the height of his powers.

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It's true the SNP would lose their prized status as the third largest party in the Commons, which might cost Stephen Flynn his two questions at PMQs every week. But that would not be seen as a failure, because it would be due to the Liberal Democrats surging to a projected 53 seats, a level at which it is almost (but admittedly not quite) arithmetically impossible for any Scotland-only party to outnumber them.

A London commentariat eagerly waiting to pronounce Scottish independence dead would instead be forced to grudgingly admit that the cause lives on.

But are Find Out Now's numbers actually plausible? Some will say they fail the smell test, if only because the projected number of seats for the Conservatives throughout Britain is just 80, which is not only far below the worst Tory result in living memory, but also poorer than most people can seriously visualise happening.

But it's worth recalling that really big landslides, even when they are foreseen, can often turn out to be more extreme than the predictions. By slumping to 165 seats under John Major in 1997, the Tories had found themselves beneath the lower bound of pre-election expectations, and few people were able to imagine the Canadian Conservatives plummeting from 156 seats to just two until it actually happened in 1993.

So the dramatic nature of Find Out Now's projection for England is not in itself a reason to doubt their positive projection for the SNP in Scotland. It's important to stress, though, that the projection does not come from a conventional full-scale Scottish poll, and therefore the numbers cannot be directly compared with the more regular polling which has frequently pointed to very troubling seat tallies for the SNP.

On the other hand, Find Out Now's numbers do not come from a tiny and meaningless Scottish subsample either. Some 18,000 respondents were interviewed across Britain for the poll, which is roughly nine times the most typical sample size of a UK poll. That was done to ensure that credible estimates of vote shares could be made at the constituency level, in Scotland every bit as much as in England.

It must also be remembered that Find Out Now's projection for Scotland is actually bang in line with one particular recent conventional Scottish poll, namely the Ipsos poll which also had the SNP on course for 40 seats. That was a rare example of a Scottish telephone poll, raising hopes that the findings may be more accurate than online polls showing the SNP slumping to well under 30 seats, sometimes well under 20.

But the reality is that the positive polls for the SNP do not actually differ all that much from the negative polls in terms of the popular vote. Humza Yousaf finds himself firmly in the scary zone where just a few percentage points in either direction will be massively magnified by the first-past-the-post voting system and have huge consequences in terms of seats.

In that sense, Find Out Now's projection does not change what we already knew, which is that the SNP could be heading for an exceptionally good or exceptionally poor General Election result, or any shade of grey in between, depending on which pollster's methodology turns out to be most accurate.