The prime minister is preparing a dramatic shift in her Brexit policy, namely an announcement that if her reworked Brexit deal is not passed by MPs on or before 12 March she will shortly afterwards give MPs a binding vote on whether or not to go ahead with a no-deal Brexit on 29 March.
This would be seen by many as a significant u-turn - because she will promise to abide by the will of Parliament, and thereby admit that a significant Brexit delay may be necessary.
As of Monday there was still uncertainty among her colleagues whether she would press the button on the volte face and put it to her Cabinet on Tuesday morning - where it will cause a furious row between Brexiters and Remainers.
The Brexiters are acutely aware that MPs would almost certainly vote to force the prime minister to delay Brexit and therefore prevent a no-deal departure on 29 March.
However absent that promise of a vote for MPs, which the PM is expected to make when addressing the House on Tuesday afternoon, somewhere between 15 and 25 ministers and parliamentary private secretaries - who hate the prospect of a no deal exit from the EU - were set to resign.
Some 23 of these government rebels - who are led by David Gauke, Amber Rudd and Greg Clark - met on Monday evening. And 18 of them made clear they were ready to rejoin the backbenchers.
Their departures would tear a devastating hole in May's government and also further undermine her ability to get any Brexit-related legislation passed.
Her u-turn on offering MPs a vote on whether to approve no-deal would be a recognition, her colleagues say, that the UK is not ready for a no-deal Brexit on 29 March.
"Preparations to avoid a severe shock to living standards and our security are simply not far enough advanced,"one said, adding that it would be impossible to eliminate all risks but much more needed to be done.
It would also be an admission that, absent such dramatic evasive action, Theresa May would not be able to avert perhaps the most painful collision of political humiliations ever endured by a prime minister.
Apart from the threatened ministerial resignations, on Wednesday MPs are set to vote for a plan devised by the senior backbench MPs Yvette Cooper, Sir Oliver Letwin and Nick Boles that would in effect rob her of the power to set the Brexit agenda.
The so-call Cooper Letwin amendment would lead to legislation, as soon as Thursday, that would compel the PM to sue the EU for a Brexit postponement, if no deal loomed, and could destroy confidence in her ability to set an agenda and govern.
So the PM and her ministers are braced for a tumultuous few days - that will go some way to determine the inextricably conjoined fates of Brexit Britain and the PM.
For the PM her pledge of a no-deal vote could deter some Tory MPs from backing Cooper Letwin and thus allow her to retain some control over the most important change to the UK in generations - but only at the price of a gargantuan u-turn, since she has consistently refused to countenance any Brexit delay.
That said, when she makes her statement to Parliament after Cabinet tomorrow, she will repeat her optimism that the EU will in the next fortnight make legally binding commitments via a so-called codicil to the Withdrawal Agreement such that the UK could not be held against its will in the controversial backstop arrangements forever.
She hopes that if the EU makes that compromise, MPs would at the last approve her deal.
But if they don’t, it now looks likely a no-deal departure won’t be the consequence - or at least not the immediate consequence.
