It was, according to the House of Commons clock, just after 2.30 in the afternoon when the nation was plunged into a constitutional crisis.

It was a crisis so severe that up to three of the roughly 15 people present when the plunging happened even looked up from their phones to mark the occasion.

What they saw was Ian Blackford, the SNP’s leader at Westminster, on his feet and talking. Two of the three quickly looked back down again.

The United Kingdom’s constitution is uncodified, relying instead on convention and precedent to gently police its internal affairs.

In his two and a half years leading the SNP at Westminster, Blackford has arguably established a convention all of his own. When Ian Blackford speaks, MPs, journalists, members of the public, catering staff and, on occasion, large items of antique furniture all understand it as the appropriate moment to evacuate the chamber.

Rumours still swirl that during an especially dreadful Ian Blackford contribution to Prime Minister’s Questions last year, a Liberal Democrat was tragically killed in the stampede.

These are the ways that rituals become ritualised. It may very well be that, centuries from now, the Palace of Westminster formally employs a Blackford, as well as a Black Rod. Blackford’s sacred role will be to stand up in the House of Commons and, while wearing his traditional dress of three-piece suit, do no more than utter the words, “Mr Speaker, the people of Scotland have spoken!” and everyone will know it’s time to go home for the day.

That, on this occasion, no one physically left the room may intimate at the seriousness of the situation. Or maybe not.

It happened at the moment at which the EU Withdrawal Agreement Bill formally received its royal assent.

“Something quite momentous has taken place with this royal assent,” Blackford said. “This is absolutely unprecedented and I say to the house that this is a constitutional crisis.”

The house, as always, took very little notice.

As chance would have it, the crisis happened seven years to the day since David Cameron – remember him? – gave his little speech at Bloomberg’s office in London, explaining how an In/Out referendum on EU membership would settle the question once and for all.

Quite what the question was, back then, no one can possibly hope to recall. But here was the question, seven years on, threatening to break up the United Kingdom.

Well, maybe it wasn’t the question doing that. What was threatening to break up the United Kingdom was Ian Blackford. It is no disservice to Ian Blackford to say that that is, quite literally, all Ian Blackford wants to do.

The problem is that the withdrawal agreement has now been given royal assent, despite the various devolved governments in Cardiff, in Belfast and in Edinburgh all declining to give their consent to it.

That, under something called the Sewel Convention, is a problem. A constitutional crisis, no less, even though it plainly isn’t. It can, quite easily, and just like Ian Blackford, be ignored.

But for nationalist politicians, there are no problems that cannot be turned into opportunities. And Ian Blackford, being a politician after all, will never turn down any opportunity to bang the nationalist drum, even if the effect of the drum is almost always to empty the room in which it is banged.

Still, you can’t blame a man for trying (though you don’t have to listen to him). The EU referendum result could hardly have been a greater gift to a nationalist cause that, in 2014, found itself suddenly wildly energised but also completely lost.

The cause of Scottish nationalism is almost like a riddle. In recent years, the Scots have shown themselves to be, by some margin, the United Kingdom’s superior people. Any country wise enough to see that both Brexit and independence are such obviously terrible ideas deserve the independence they do not want. (They don’t deserve Brexit, of course. No one deserves that.)

It’s a mess, Brexit. And it’s deeply unfortunate that Scotland said no to it but are going to have to do it anyway. But it’s not a crisis. The only people who want a crisis are the SNP.