Stephen Flynn, the SNP leader in Westminster, rose from his spot on the green benches and twirled his black coat onto his shoulders.

So began one of the most extraordinary scenes the Commons has witnessed in years, as scores of MPs joined him in a walkout from the chamber.

First, the SNP began to file out en masse. Then, watching their Scottish adversaries exit, dozens of Tory MPs decided to follow suit.

Dame Rosie Winterton, the deputy speaker, watched the chamber empty in bewilderment as the result of a decision the speaker Sir Lindsay Hoyle had made hours earlier.

Labour MPs pounced. One shouted “call yourself a government?” across the void to those jockeying to leave. “What a rabble,” pronounced another.

Sir Chris Bryant, a shadow culture minister, was left to make a point of order facing row after row of deserted green leather benches opposite.

The walkout was the dramatic high point of an afternoon of Commons chaos sparked by Sir Lindsay’s controversial decision to pick a Labour amendment on Gaza.

Its seeds had been sewn some seven hours earlier when the Speaker had unexpectedly been confronted by Sir Keir Starmer in his office.

All morning, after a night of little sleep, he had faced mounting pressure from political parties over which Gaza amendments to select for votes.

The lobbying from Labour, the Tories and the SNP for their proposals - each with a differing form of words calling for a stop to the fighting - was led by the party chief whips.

Alan Campbell for Labour, Simon Hart for the Conservatives and Owen Thompson for the SNP talked to Sir Lindsay in person trying to persuade him.

However, as the morning went on and the decision point drew closer, Sir Lindsay, huddling with his clerks in the Commons, received an unexpected visit.

The Telegraph can reveal that Sir Keir went to see the Commons Speaker personally to make his case.

The visit was unusual. Normally matters of Commons business and votes are left to the whips, the traditional connecting point between a political party and the parliamentary authorities.

No other political leader, not Stephen Flynn, the SNP leader whose party had called the vote, or Rishi Sunak, the Conservative leader and Prime Minister, visited the Speaker.

But it is Labour whose MPs are more split on the Israel-Gaza conflict than political rivals.

And it was the Labour leader who felt he had to personally make his case to Sir Lindsay.

The conversation lasted just a few minutes. In it, Sir Keir is understood to have urged the Commons leader to select the Labour amendment for a vote.

Sir Keir is understood to have said, “emotions are running very high”, or words to that effect, according to a source familiar with the discussion.

The decision to personally lobby the Commons Speaker was eye-catching for another reason. Sir Keir leads the party which Sir Lindsay represented as an MP for two decades.

From 1997 to 2019, Sir Lindsay was a Labour MP, seeking election under the party banner and representing Chorley.

Only in 2019, upon becoming Speaker, did he give up party allegiance, as is traditional when taking on the role.

How firmly did Sir Keir lean on Sir Lindsay? The conversations were about the substance, sources close to both figures have said.

An allegation some Labour figures had made clear to the Commons Speaker that he would be forced out after the election should he not pick Sir Keir’s amendment was dismissed as “rubbish” and “completely untrue” by a Labour spokesperson. Figures close to Sir  Lindsay echo the same point.

Sir Lindsay also had to deny on the record that he had met Sue Gray, Sir Keir’s chief of staff, after a Tory MP tweeted she had been seen in the Commons.

For the Commons Speaker, the security of MPs and the need to let all sides of the debate have a say were his driving motivations, according to his allies.

“He would have seen any party leader who asked to see him,” said a supporter of Sir Lindsay.

The Speaker had to hot-foot it from the ill-fated meeting to the Commons to make the announcement that would throw his future into doubt.

He rushed into the chamber and turfed one of his deputies, Sir Roger Gale, out of the chair with just minutes to spare before the debate started.

But he was barely 30 seconds into his speech when dissent began to spread across the green benches as it dawned on MPs just what he had decided.

It began with gasps among MPs as, peering over his glasses, he read from a script that he wanted to present them with the “widest possible range of options”.

He frowned at the Tory benches from behind his papers and ploughed on, but things were about to get much worse as the bewilderment turned into anger.

“Just let me finish,” he pleaded, as backbenchers began to kick up a fuss.

When he tried to explain there was a precedent for his actions, one shouted: “When?” Another made their feelings plainer still, yelling: “You’re moving the goalposts.”

By this point, he had already lost the chamber. But it was the end of his speech that made it plain just how badly he had misread the mood of Parliament.

Sir Lindsay had begun his speech by admitting his decision to circumvent convention was “exceptional” but justified given the “highly sensitive subject”.

He ended it by arguing that those same rules he had chosen to discard were archaic and deprived MPs of the chance to debate multiple points of view.

At his mention of the word “outdated” the chamber descended into a cacophony of jeers, laughing and heckling from both sides of the divide.

The ruckus didn’t stop for an excruciating 30 seconds, during which time the helpless Speaker battled in vain to get his voice heard above the din.

As he battled to the end of his statement, at times stumbling over his words, the SNP benches roared into life with outrage at what he had done.

He was immediately taken to task by Owen Thompson, the party’s chief whip. “What is the point of an opposition day if it’s going to be done like this?” he demanded.

His colleagues applauded in response, flouting a strict ban on clapping, but received only the mildest rebuke from a stunned Sir Lindsay.

The Speaker left the chair shortly as those MPs in the chamber turned to the substance of the debate, and those outside turned to their mobile phones.

Social media swiftly lit up with criticism from angry Tories. Sir Michael Fabricant, a former whip, said he had caused “a constitutional crisis” with the “unprecedented” decision.

Dame Jackie Doyle-Price, an ex-minister, added: “This is a bad day for Parliament. Conservatives should always defend constitutional precedent.”

Their fury was fuelled further when Parliament published a letter to Sir Lindsay from Tom Goldsmith, the Clerk of the House, revealing he had advised him his decision would go against the normal rules.

Everything changed again at just after 6pm when Penny Mordaunt, the Leader of the Commons, announced the Tories would be withdrawing their amendment.

“I fear that this most grave matter that we are discussing today and this afternoon has become a political row within the Labour Party and that, regrettably, Mr Speaker has inserted himself into that row and undermined the confidence of this House,” she intoned.

The announcement mattered because, with the Government no longer opposing the SNP motion, it would mean Labour’s amendment was destined to sail through.

Soon, Tory MPs began to demand to know where the Speaker was, to which Dame Rosie replied that he would not be returning until Thursday.

A visibly furious Mr Flynn rose and thundered: “Where on earth is the Speaker of the Commons and how can we bring him to this House?”

The mass walkout then ensued, followed by bizarre scenes 10 minutes later when those MPs left were asked to vote on whether to sit in private.

William Wragg, a Tory backbencher, launched the ploy in an attempt to delay matters, exploiting a Commons rule that votes on opposition day debates are invalid after 7pm.

The vote on it ate up a further 15 minutes and was rejected, but in any case, it failed to stop Dame Rosie from calling a vote on Labour’s amendment.

Labour MPs shouted “aye” loudly and the deputy speaker declared that it had passed without the need for MPs to record their votes individually.

But later, MPs from other parties insisted they had shouted out to oppose the amendment, meaning there should have been a division called.

The SNP’s woes were then further added to when they were denied the opportunity to cast individual votes on their motion, despite it being their opposition day in the first place.

Around 7pm, there was another moment of high drama when Sir Lindsay - who had previously refused to appear - returned to his chair.

He apologised for his actions and explained he had made his decision because he was concerned about the security of members.

Speaking as thousands of pro-Palestinian protesters massed in Parliament Square just 200 yards away, he said: “I regret with sadness that it has ended up in this position. It was never my intention.

“I was absolutely convinced that the decision was done with the right intentions. I recognise the strength of feeling of members on this issue.”

Mr Flynn was unassuaged, accusing him of treating the SNP with “utter contempt” and adding: “I will take significant convincing that your position is not now intolerable.”

As the evening drew to a close Sir Lindsay was hit by a further blow as it emerged that 33 MPs - 22 Tories and 11 SNP - had signed a motion of no confidence in him.