Outside the House of Commons thousands gathered to mark the Brexit Day that never was.

There were flags, placards, pipe bands and singing as pro-Brexit campaigners swamped Parliament Square.

Chants of “Oh Tommy Robinson” sprang up for the controversial figure as former Ukip leader Nigel Farage told the crowds that March 29, which he said should have been a day of celebration, was now a day of “great betrayal”.

And inside the House of Commons, Theresa May was contemplating her own exit day after suffering a third humiliating parliamentary defeat.

Yet the Prime Minister was still clinging to the faintest hope her withdrawal agreement could be passed in the two weeks that lie ahead until, potentially, the new Brexit Day of April 12.

Amid more dramatic scenes, MPs voted by 344 to 286 against Mrs May’s plan – a majority of 58.

The defeat was less than the previous ones of 230 and 149, which led one Downing Street insider to say: “The PM still believes her deal is the best outcome and we are seeking a way forward.”

In the coming days, Mrs May and her ministers will continue to speak to MPs and, crucially, to Northern Ireland’s Democratic Unionists.

But after the defeat was announced, the PM told MPs: “I fear we are reaching the limits of this process in this house.”

Some are interpreting that remark as a warning that if MPs back an option she cannot support, or fail to agree on an alternative, she is ready to call a general election.

European Council President Donald Tusk called an emergency summit of EU leaders for April 10 to discuss the implications of the Brexit deadlock and ask Britain for its next steps.

The prospect of the Government asking for a longer delay has risen sharply. A further extension is likely to be for at least a year with strings attached, including financial ones.

A parliamentary order will have to be passed to facilitate Britain taking part in the May European elections.

It is also not certain a longer extension would be granted.

The 27 member states would have to agree unanimously. If it were not, the UK would crash out of the EU in two weeks. On Monday, Parliament will again seek to find consensus around an alternative plan.

Earlier this week, all eight options were rejected but the two with the largest votes were a customs union and a confirmatory referendum.

One possibility is a “run-off” between whatever alternative option gets the most support in a second round of “indicative votes” and the PM’s plan, possibly including Labour demands to give Parliament a greater role in the second phase on Britain’s future relationship with the EU.

The crunch debate and vote came on what otherwise would have been a non-sitting Friday. Mrs May, referring to her personal decision to step down early, appealed to MPs, saying: “Every one of us will have to look into our hearts and decide what is best for our constituents and our country.”

Labour’s Yasmin Qureshi intervened to say: “Brexit – the withdrawal agreement and the referendum – has always been about the Conservative Party.” And the SNP’s Stewart McDonald questioned why the PM had not given Scotland the sweeping reforms and devolution on jobs and welfare it needed to mitigate against the effects of Brexit.

“Instead, she stuck her head in the sand and that is why she has got nowhere with the Scottish Government or the Scottish National Party,” insisted the Glasgow MP.

Mrs May hit back, saying: “The Government have given the Scottish Government extra powers and they are not using them; except, of course, the power to increase taxes in Scotland more than in the United Kingdom.”

As the division bell rang, Tory whips could be seen cajoling one colleague into the aye lobby. But it was not enough. The Government’s expected defeat was confirmed minutes later.

The PM said the result should be a “matter of profound regret” for all MPs as the implications for Britain were “grave”.

But Mrs May added: “This Government will continue to press the case for the orderly Brexit that the result of the referendum demands.”

Jeremy Corbyn appealed to the PM to accept her deal was dead and an alternative had to be found.

“If the Prime Minister cannot accept that, she must go, not at an indeterminate date in the future, but now, so we can decide the future of this country through a general election,” added the Labour leader.

Ian Blackford for the SNP echoed the point. He said Parliament now had to seriously consider scrapping Brexit altogether, stressing: “We need to apply a handbrake to this process.”

The Highland MP told Mrs May: “She has indicated her departure. She should now go and we should have a general election.”