MPs voted against eight Brexit alternatives after John Bercow warned Theresa May is not guaranteed to be allowed a third meaningful vote on her deal.

Labour former minister Dame Margaret Beckett's proposal for a public vote before ratification of any Brexit deal polled the highest number of votes among MPs, while Tory Father of the House Ken Clarke's customs union plan was defeated by the lowest majority.

But the first day of the indicative vote process failed to find a proposal which commanded a Commons majority, with its developer Tory former minister Sir Oliver Letwin saying it was a 'very great disappointment'.

But Sir Oliver said those behind the procedure had predicted such a scenario and they hoped a majority view will be reached on April 1, when a second day of indicative votes is expected.

MPs also formally voted to change the exit day of the UK's withdrawal from the EU from March 29 by 441 votes to 105, majority 336, with 93 Tories among those who opposed it.

A lengthy day of Brexit drama in the Commons burst into life earlier on Wednesday as Mr Bercow issued a fresh warning that substantial changes are required to allow a third meaningful vote on Mrs May's Brexit deal.

The Commons speaker insisted the government must 'meet the test of change' having previously ruled that another meaningful vote would not be accepted for consideration without substantial changes, which he indicated should include a negotiated change with the EU.

His remarks came before Brexit Secretary Steve Barclay revealed the government would table a motion to enable the Commons to sit on Friday as it bids to secure approval for its deal.

After the indicative votes, Mr Bercow maintained his stance although suggested he was open to persuasion on whether the current circumstances had changed enough to allow a third vote.

Referring to the EU documents in the second vote, he said: 'Those were examples, it seemed to me, of facts, of evidence and of circumstances that were relevant.

'I note the opinion... that the situation has in some way now changed.

'One has to look at the specifics and if people come with specifics, then the specifics are considered.'

What happens next?

Theresa May has promised to fall on her sword if Tory rebels back her deal - but will they take her up on the offer?

And after MPs failed to find a majority for alternatives to her plan, what next for Brexit?

• The prime minister's deal could return

The UK was due to leave the European Union on Friday, but instead it could be the day Mrs May tries to make it third time lucky for her Brexit deal.

The Commons was not expected to sit on March 29, but Brexit Secretary Stephen Barclay said plans were being made for that to happen because 'it's better to have it and to not need it, than to need it and not have it'.

But Commons speaker John Bercow could throw a spanner in the works after he again stressed that there would have to be substantial changes before he would allow another vote on an issue that had already been considered.

• Resistance to the deal has weakened, but is it enough?

Brexit standard-bearer Boris Johnson, who once compared Mrs May's deal to a 'suicide vest' wrapped around the British constitution, told the European Research Group of Tory MPs he will now back it.

Other Eurosceptics previously opposed to the deal have also reluctantly swung behind it because they fear the alternatives are now softer forms of Brexit or the possibility of not leaving the EU at all.

But the Democratic Unionist Party remain opposed, with leader Arlene Foster saying she could not sign up to a deal that 'threatens the union' of the United Kingdom.

The DUP's continued opposition means that some Tories, including Jacob Rees-Mogg, will also refuse to back the deal.

• What about the prime minister?

Mrs May told MPs: 'I know there is a desire for a new approach - and new leadership - in the second phase of the Brexit negotiations - and I won't stand in the way of that.'

But in order to get to that 'second phase', her deal would have to pass. It remains to be seen whether her commitment to leave office is enough to win over wavering rebels.

Mr Rees-Mogg acknowledged that if her deal did not get through then 'she would have every right to carry on'.

But a third defeat - or ducking another vote entirely - would surely cause further damage to her crumbling authority.

• So when will the UK leave the European Union?

Unless the Withdrawal Agreement is passed by MPs by the end of the week, Brexit day is set for April 12. This is the final day on which the UK can set out its next steps to the European Council, if it wishes to be granted a longer extension. If it does not do so, the UK would crash out without a deal.

If Mrs May finally gets her deal through Parliament the UK will leave on May 22.

• And when will Mrs May leave Number 10?

Once the Withdrawal Agreement is passed, the government needs to rush an implementation bill through parliament, along with other legislation needed to ensure a smooth departure. It is unclear whether Mrs May would delay her resignation until this process is complete and the UK formally leaves on May 22.

It would be possible for her to declare she is stepping down, but to remain in post during the contest to select a successor.

If she remains in office until May 25, she will overtake Gordon Brown's tenure of two years and 319 days in office to become the 35th longest-serving PM in British history. If she lasts until May 26, she outstrips the Duke of Wellington and another 28 days to June 23 will take her past Neville Chamberlain.

She is due to represent the UK at the annual G20 summit in Osaka, Japan, on June 28 to 29, which could be her last outing on the international stage before stepping down.

• Will there be more indicative votes?

After Wednesday's votes failed to produce a majority for any of the eight options under consideration, more time has been set aside on Monday, April 1.

Sir Oliver Letwin, architect of the plan to seize control of the Commons timetable, said: 'If on Monday the House is able to reach a majority view, I think that would be in the interests of our constituents.'

And what about the petition to revoke Article 50?

The government has rejected a petition calling for Brexit to be stopped, which is approaching six million signatures.

The petition is due to be debated by MPs on April 1, after smashing the 100,000 threshold for consideration and becoming the best-supported proposal in the history of the House of Commons and Government's e-petitions website.

Rejecting the oft-repeated claim that EU withdrawal is the 'will of the people', it calls for the revocation of the Article 50 letter informing the European Council of the UK's intention to leave.

The Article 50 letter can be withdrawn by the UK unilaterally, without the need for EU agreement, leaving Britain free to continue as a member on its current terms.

But in its official response to the petition, the Department for Exiting the EU said: 'It remains the government's firm policy not to revoke Article 50. We will honour the outcome of the 2016 referendum and work to deliver an exit which benefits everyone, whether they voted to leave or to remain.

'Revoking Article 50, and thereby remaining in the European Union, would undermine both our democracy and the trust that millions of voters have placed in government.

'The government acknowledges the considerable number of people who have signed this petition. However, close to three-quarters of the electorate took part in the 2016 referendum, trusting that the result would be respected.

'This government wrote to every household prior to the referendum, promising that the outcome of the referendum would be implemented.

'17.4 million people then voted to leave the European Union, providing the biggest democratic mandate for any course of action ever directed at UK government.

'British people cast their votes once again in the 2017 General Election, where over 80% of those who voted, voted for parties - including the opposition - who committed in their manifestos to upholding the result of the referendum.

'This government stands by this commitment.

'Revoking Article 50 would break the promises made by government to the British people, disrespect the clear instruction from a democratic vote, and in turn, reduce confidence in our democracy.

'As the Prime Minister has said, failing to deliver Brexit would cause 'potentially irreparable damage to public trust', and it is imperative that people can trust their Government to respect their votes and deliver the best outcome for them.'

The petition will be debated by MPs in the Commons' secondary chamber Westminster Hall. A government minister will be required to respond to the petition, but there will be no vote on the action it demands.

MPs will also debate a petition calling for a second EU referendum, which has received more than 120,000 signatures, and another - signed by more than 140,000 - demanding that the UK leave with or without a deal on March 29.