An extraordinary sitting of the British parliament on Saturday, billed as a landmark day in the country’s Brexit saga, resulted in Prime Minister Boris Johnson sending a letter to the EU requesting an extension to the UK's exit date. The House of Commons voted by a margin of 322 to 306 in favour of the so-called Letwin amendment, a significant blow to Mr Johnson’s hopes of quickly passing his new Brexit deal through parliament. However, the vote did not deliver the outright defeat of Mr Johnson’s agreement with the European Union. That vote will now not go ahead until next week after Conservative MPs abruptly walked out of the chamber following the reversal. The amendment, made by former Tory MP Sir Oliver Letwin, was introduced to withhold approval of the government's Brexit deal until legislation to enact it had been passed in its entirety. Mr Johnson was defiant in his response. "Alas, the opportunity to have a meaningful vote has effectively been passed up because the meaningful vote has been voided of meaning,” he said. "But I wish the House to know that I am not daunted or dismayed by this," he went on. “I continue in the very strong belief that the best thing for the UK and for the whole of Europe is for us to leave with this new deal on October 31.” The truncated exchange in the Commons following the defeat centred on whether Mr Johnson was legally required to ask the EU for an extension. The British leader has said, “do or die”, that he would take Britain out of the EU on October 31. “To anticipate the questions that are coming from the benches opposite, I will not negotiate a delay with the EU," the prime minister added, claiming he was under no legal obligation to do so. The leader of opposition Labour party, Jeremy Corbyn called on the prime minister to rethink his statements. "Today is a historic day for parliament because it has said it will not be blackmailed by a prime minister,” he said. “I invite him to think very carefully about the remarks he just made about refusing apparently to apply for the extension which the EU number 2 Act requires him to do," Mr Corbyn added. British government source revealed to multiple media outlets on Saturday evening that Mr Johnson had sent an unsigned letter to the EU requesting a Brexit delay and a separate note saying that he did not want an extension. EU Council President Donald Tusk confirmed on Twitter he had received the delay request. The Letwin amendment, introduced earlier this week, was proposed as an insurance policy to ensure the UK did not crash out of the EU on October 31 without a deal. Under the terms of the so-called Benn Act, if an agreement on a deal on Saturday was not forthcoming, the prime minister was required to seek a further extension to the withdrawal process from the EU until the end of January. The prime minister’s office had earlier threatened to pull the rug out from under proceedings in the face of the Letwin amendment. Even before the first remarks in the House had been made, Downing Street warned that it would send Tory MPs home if the amendment passed. Downing Street briefed that voting for the Letwin amendment was a vote for delay and pointed out the irony of parliament opting to render the extraordinary Saturday sitting – the first since the 1980s –meaningless by kicking the can further down the road. Aside from the legislative manoeuvres, the vote over Mr Johnson’s deal, which is now scheduled for Monday, appeared too close to call. The prime minister secured the assent of much of the hard-Brexiteer European Research Group (ERG), which had so often frustrated the ambitions of his predecessor Theresa May. “Let's #GetBrexitDone. No more delays and indecision. With absolute resolve, we can be a great independent country through this deal,” Steve Baker, the ERG chairman, tweeted. Earlier he had indicated that not only would the ERG vote in favour of the deal but support all legislation needed to enact it. The government also appeared to have secured the votes of many, but by no means all, of the Tory MPs from whom the government whip was withdrawn over the Benn Act. These gains needed to overcome the loss of support from Mr Johnson’s once-close allies, Northern Ireland's Democratic Unionist Party (DUP). Since it was announced in Brussels days ago, the DUP has railed against the deal, saying it would adversely impact the Northern Irish economy and threaten the Good Friday Agreement, the 1998 peace accord to end violence in the country. Outside Westminster, as MPs voted, hundreds of thousands of anti-Brexit protesters demonstrated their opposition to Mr Johnson’s deal. The marchers, who are demanding a second referendum on Britain’s exit from the European Union, raised a resounding cheer when the results of the government defeat were delivered.