After the prime minister was threatened with what could have been a damaging commons defeat, she promised key concessions in dramatic last minute talks with pro-EU rebels.
It is likely to mean her accepting a deadline by which she must secure a deal with Brussels, if she wants to stay in the driving seat for negotiations.
Her ministers must now spell out the detail of her compromises within days, with Tory rebels warning a failure to do so would reignite the prospect of a major commons loss destabilising her leadership.
It followed a day which started with the resignation of a minister and passed into febrile commons debate that saw ministers bargaining openly with rebels in the chamber.
Rebel MP Nicky Morgan told The Independent: “The whole point of what has come about is that we are going to have a process to this, something which does not simply allow us to drift into a hard Brexit.”
The row was precipitated by the Lords last month passing a plan that would have given parliament the power to direct Ms May’s actions if she failed to seal a Brexit deal later this year.
Ministers were demanding Tory MPs vote it out of existence in the Commons on Tuesday, but had also refused to consider a more palatable compromise proposed by the former Conservative attorney general Dominic Grieve.
It would have instead seen Ms May being tied into a strict timetable of having to set out her own proposals if she failed to seal a deal by November, and then gain parliamentary approval for them – the stronger powers for MPs to direct her action would only come into play if a deal had still not been reached by February.
But Ms May’s tough approach was dealt a heavy blow when at 7am on Tuesday she opened a resignation letter from junior minister Phillip Lee, who quit because he said the government was overlooking “parliamentary sovereignty” in its approach to Brexit.
As government whips spoke with MPs it began to become apparent they were heading for a defeat, which would have seen the commons enshrine the tougher Lords plan in law, effectively stripping Ms May of her executive power.
As the need to compromise grew, solicitor general Robert Buckland strenuously tried to persuade Tory rebels not to defy the whip and reassure them the government was listening.
Chief whip Julian Smith could also be seen darting in and out of the chamber and between Tory backbenchers, before becoming locked in a discussion with Mr Grieve.
But with the result still hanging in the balance, Ms May then made a personal last minute intervention to avert a disaster, calling around 17 rebels into her office shortly before the crunch vote.
One MP said: “It was real last minute stuff, she knew she was going to lose and had no choice.”
Another said: “She promised to go along with the spirit of Dominic’s plan – we will be looking for a set timetable, if not specifically by November and February, then some kind of specific timescale by which she must seek parliament’s approval for her plans in the case of no deal being reached.
“If we don’t get that by next week then we will be back where we are today, and the government will be facing the prospect of the Lords amendment being passed – there are enough of us to do it and they know it.”
Senior backbencher Sarah Wollaston said the prime minister had given way because there was “a very strong possibility that the government might lose the vote”.
She added: “We want to see parliament having the power to stop a hard, walkaway, no deal Brexit.”
Mr Grieve said the parts of his amendment he now expects to be brought forward by ministers include the November deadline.
He explained: “The prime minister agreed that the amendments we tabled, and the issue that we had raised about parliament’s role in the event of no deal, was an important one, and undertook to work with us to put together amendments to present in the Lords which would address those concerns.”
The prime minister’s intervention mean rebel MPs allowed the government to defeat the Lords plan last night, but it will now be returned to the upper chamber where it is likely be approved again.
The government can only avoid that if it now brings forward its own proposals along the lines agreed between Ms May and the rebels on Tuesday.
A government source said ministers are likely to give way on a form of the November deadline and agree to giving MPs the chance to veto her plans, but could not agree to the idea of allowing parliament to directly dictate them.
Following the vote, shadow Brexit secretary Sir Keir Starmer said: “Facing the prospect of a humiliating defeat Theresa May has been forced to enter negotiations with her backbenchers and offer a so-called concession.
“We will wait and see the details of this concession and will hold ministers to account to ensure it lives up to the promises they have made to parliament.”
Liberal Democrat Brexit spokesman Tom Brake said: “As has become a tradition in Brexit negotiations, the Tories have been forced to cobble together a compromise.
“Time will tell as to whether this is just another attempt to buy off the rebels or a real attempt at consensus.”