It was one way of getting noticed. For a while now the SNP have been feeling rather peripheral to the main events in Westminster. Unloved, unrecognised, unwanted. An afterthought at best. Much the same way the prime minister must feel when she goes to meetings of the G5 + 1 + 1 and the European council.

After parliament had been given just 19 minutes the day before to debate the impact of Brexit on the devolved governments, Ian Blackford decided enough was enough at prime minister’s questions. Rather than bothering to ask Theresa May a question she wasn’t going to answer, the SNP leader chose to invoke an arcane piece of procedure to demand an immediate vote in private on the government’s handling of Scottish constitutional affairs. For the first time in his parliamentary career, Blackford had the Commons’ undivided attention.

SNP MPs walk out of Commons in protest over Brexit debate Read more

Cue chaos. The Speaker was blindsided and didn’t appear to know whether he was obliged to halt PMQs and call a vote immediately or delay it till the end of the session. After some hesitation, John Bercow advised Blackford to wait until PMQs were over. Blackford remained on his feet, insisting the session be interrupted for his meaningless meaningless vote. As a change from a meaningless meaningful vote if nothing else.

With the noise levels rising and sensing he was about to lose control of the chamber, the Speaker ordered the SNP leader in Westminster to leave the chamber for the rest of the day. Blackford punched the air. Job done. The vote in private had always been secondary to the stunt in public. Now he couldn’t be ignored. Even if only for a matter of minutes.

As Blackford waddled – he tried to stomp, but was just a bit too self-conscious – out of the chamber, the other 34 SNP MPs rose to leave with him. Joanna Cherry gestured angrily towards the Speaker. Mhairi Black jabbed her finger and looked ready to take on all comers – “come and get me if you think you’re hard enough” – as Tory backbenchers heckled and jeered the Scots Nats on their way out.

The walkout might have been right up there in futility with the Lib Dem hissy-fit of 2008 – over an EU referendum, of all things – but the long-term fallout may be more damaging. The sight of several hundred entitled Tory backbenchers making it clear they don’t give a toss about anyone in Scotland is not going to play out well north of the border. When it comes to the Union, the Tories couldn’t have made it clearer that it’s England first.

The disruption did work to one person’s advantage though. For a few minutes everyone forgot about the prime minister. There’s only one reasonable explanation left for how Theresa May can continue to function. And that is that she goes to bed each night hoping everyone will forget how badly she’s screwed up the day before and that she can start afresh in an altered reality. One where she never called the election. Where Britain never voted to leave the EU. And preferably where she isn’t prime minister.

For the fourth consecutive week, Jeremy Corbyn chose to exploit the government’s divisions and confusion over Brexit, though with less success than before. Not because May was any better prepared, but because her uselessness has now been factored in to the equation. No one now expects her to say anything coherent – or even credible – and provided she doesn’t fall over or inadvertently crash her circuit boards, her minders rate her performance as a triumph.

Better still for May, the mass walkout meant she didn’t have to face tricky questions from the four Scots Nats who had been tabled to speak. Instead the hardline Brexiters Jacob Rees-Mogg and Philip Davies got to press her on whether she was going to offer concessions to the Tory rebels who forgot to rebel or stick with offering a meaningless meaningful vote.

May happily reassured them. She is now so far gone with Stockholm syndrome she can’t prevent herself from saying anything she thinks her captors want to hear. Whether she meant what she said, not even she really knows. It was just beginning to dawn on Dominic Grieve that he might have been outwitted by someone far dimmer and less capable than him.

To round off one of the more extraordinary PMQs, Labour’s Frank Field spent the entire session sitting on the Tory front bench. He has appeared for a while to be angling for a transfer. Now he’s got his wish. If several more Tory ministers resign over Brexit, he could be in the cabinet by this time next week.