Tuesday Nov 30 is the feast of St Andrew, the patron saint of Scotland (and Russia, Greece, Ukraine and a host of other countries). In recognition of the date, the main business in the House of Commons has been given over to an Opposition Day for the Scottish National Party.

Opposition Days are an opportunity for Labour and the other minority parties to highlight issues high up their agenda. We learned at the weekend that the SNP’s Westminster leader, Ian Blackford, intends to table a motion of censure against the Prime Minister, to concentrate the focus of the House on his personal failings as leader of Her Majesty’s Government. A cynic might note that the party has chosen not to debate a policy area such as education, health or welfare; certainly nothing that in Scotland is a devolved matter.

Blackford is not a man short of bluster. When he rises to speak at Prime Minister’s Questions on a Wednesday, there is an audible groan from all sides of the House. Addressing his party’s conference on Sunday, he spoke of the SNP providing the “real opposition” – quite a boast for a party with 45 MPs in a House of 650, clearly intended as a slight at Labour’s lacklustre performance.

“Unless he faces consequences for his disastrous actions, he won’t just think he’s gotten away with the mess he has made of the last few months – he will think he can do it all over again,” Blackford went on.

The SNP then tweeted that the motion to be debated on Tuesday would underline the fact that Scots had “no confidence” in Boris Johnson’s leadership.

There was a swift ‘clarification’. While the SNP seeks to demonstrate “no confidence” in the Government, it is not – as some incautious souls may have incorrectly assumed – tabling a motion of no confidence. Instead, Blackford will table a ‘motion of censure’, a broader and less formal instrument which usually comes in the form of an Early Day Motion. Motions of no confidence have specific consequences, and that is emphatically not the SNP’s style.

Why does this matter? Because it is all related to Blackford’s mention of “consequences”. Quite apart from the Prime Minister facing them, it is the SNP leader who is afraid of them. He knows that a motion of censure will be defeated, and defeated heavily. Previous such motions, against Chris Grayling and Esther McVey during their time in cabinet, were soundly rejected. Confidence motions are serious constitutional business, and can lead to the collapse of governments. This ‘censure’ motion is just parliamentary chaff.

Fair-minded readers might then wonder why Blackford would wish to pursue such an obviously doomed strategy. Is he some kind of latter-day Lord Raglan, ordering his troops into a disastrous action which can only end in defeat? Yes and no. Blackford knows that he does not have the numbers even to alarm the government. Johnson’s working majority is 77, so even the official opposition is powerless under normal circumstances.

In the tartan-blinded world of the SNP, however, Blackford does not need to win. By choosing a motion of censure, he avoids taking on the government on central policy areas like education or health: areas in which the SNP administration in Edinburgh is failing badly. Nicola Sturgeon, the First Minister, twists and turns to avoid defending her record in office, preferring to concentrate on independence, the great panacea, and the supposed evils of the government in Westminster. So Blackford will try not to open his substantial flank to that kind of criticism.

The focus will be Boris, Boris, Boris, because the Prime Minister’s personality and style are held to play less well in Scotland than they do south of the border. A recent poll found his approval rating to be -62, even worse that Sir Keir Starmer (-35). So, the SNP’s logic goes, play the man, not the ball.

And heavy defeat in parliamentary terms suits Blackford too. It reinforces the idea of “them and us”, of Westminster against Scotland, of the SNP as a brave band of freedom fighters against the political establishment. Never mind that they have occupied Bute House, the official residence of the first minister, for 15 years. Scottish history is, in any event, littered with ‘noble’ defeats: Halidon Hill, Flodden, Solway Moss, Culloden.

Ian Blackford knows what he is doing. Tomorrow he will line up his small band against the government’s big battalions, and, in parliamentary terms, it will be a massacre. But that suits him. For it stokes the fires of grievance, drives a wedge between the Scottish electorate and the government, and performs a vital act of prestidigitation. Look not at our record, goes the SNP war cry, but at our enemies.