IT all started so sedately.

There he was the urbane, softly-spoken SNP Bagpuss gently complaining about how those nasty, horrid Tories had “silenced Scotland’s voice” over the Brexit Bill.

Slowly, Ian Blackford’s indignation about Whitehall’s power-grab unfurled itself.

By the time he was onto the discourtesy and disrespect shown to Scottish MPs over the lack of debate, the Highland MP was more like a wounded lion.

Watch: Ian Blackford leads dramatic SNP walk-out from Commons

After Thezza rose to blame the lack of debate on the bill on those scurrilous socialists for tabling meaningless votes, the Highland MP had had enough and, to the surprise of the whole House, demanded a vote to turn PMQs into a private session. What?

A flummoxed John Bercow looked at the Commons lawyers; the lawyers looked back. A piece of paper was quickly produced and a lawyerly finger pointed something out. The Speaker insisted he was not obliged to consider Mr B’s request. But the SNP chief stood his ground.

The chamber’s noise increased. “Order,” shouted the Speaker, admitting: “I have had a mixed sequence of advice. Order. This has not happened before.”

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After taking more legal advice, Mr Bercow declared he was calling the vote after PMQs. “That is the end of the matter,” he confidently declared. But it wasn’t.

When the PM stood to speak, so too did the chief Nat. “No,” barked the Speaker, “you are not moving anything. Resume your seat!” Mr B sat down, then stood up again.

The SNP’s fresh-faced David Linden shouted repeatedly: “Now!” earning Mr Bercow’s wrath.

After the chief Nat rose again, to applause from some of his own side, one or two Tory MPs could he seen signalling to the Chair to kick Mr B out of the chamber; seconds later, the Speaker did just that.

As the SNP champion puffed out his chest and moved to exit, his Nationalist followers rose as one and began filing out.

One, Joanna Cherry, waved a lively goodbye to Mr Bercow while her parliamentary chum Mhairi Black angrily stabbed her finger at some barracking Tory MPs.

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After the Nationalists had performed their grand display of choreographed anger, Conservative backbencher Luke Hall was called to speak and quipped to laughter: “Given the number of people who are leaving the Chamber, I feel as though I am making one of my after-dinner speeches.”

Once the high drama had subsided, Mr Bercow, who branded the SNP's act of defiance a stunt, looked up at the public gallery and noticed the youngest member of the audience.

“For all the turbulence and discord of today’s proceedings,” he noted, “the little baby who has been observing them has been a model of impeccable behaviour; from start to finish.”