It has long been speculated that Theresa May will one day face a no confidence vote of her own Conservative MPs.
Rumours about plans to oust her in this way have circulated in Westminster for more than a year, and she has consistently refused pressure to resign - meaning a no confidence vote remains the only way to depose her.
A vote of no confidence is more likely than ever before following the fallout from Ms May's Brexit withdrawal proposal.
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Previously, couple of Tory MPs, Andrew Bridgen and James Duddridge, have made public the fact that they have submitted no confidence letters, with Duddridge announcing his just moments before her speech at this year’s party conference.
Since then, Jacob Rees-Mogg, a prolific Brexiteer has announced he's sent a motion of no confidence against the Prime Minister. It is expected that more members of the European Research Group, which Rees-Mogg is the Chair of, will also move to see a vote of no confidence in the Prime Minister.
How many letters have been submitted?
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The only man who actually knows is Sir Graham Brady, the Chair of the 1922 Committee of Backbench MPs - and he is the last word in discretion.
He keeps the letters in a safe, and no one gets to see.
Meanwhile, is in the interests of those who want to remove the PM to make it seem imminent, so there is a lot of spin.
But there is rarely this much noise in Westminster - for such a sustained period - without some truth being in it. In other words, where there's smoke there's fire.
Some MPs now think Theresa May could face such a vote within weeks, or even days.
What happens to trigger a no-confidence vote?
Only Conservative MPs get to vote. There are 316.
15% of them - 48 MPs - need to submit letters to trigger a no confidence vote.
Triggering a vote does not mean there will automatically be a leadership contest - because Theresa May could win.
When 48 letters are received, Sir Graham Brady will announce the fact in the Commons, but it’s likely that the news would leak before then.
Brady then meets the PM to decide the date for the vote.
It has to be held 'as soon as possible’, likely within a matter of days.
The text of the motion would probably read: "That this House has no confidence in HM Government."
Theresa May needs half of Tory MPs - 159 - to vote against the motion in order to remain Prime Minister.
If she wins, there cannot be another no confidence vote for another calendar year.
What happens if Theresa May loses?
If she lost, Theresa May must announce that she will resign and she would be barred from standing again in the next leadership contest.
There would then immediately be that Tory leadership contest.
If there is more than one candidate (there will be) then there are a series of first past the post votes among Tory MPs to eliminate the field until two candidates remain.
Depending on how many candidates stand, this part of the process is relatively quick.
Those two candidates then face a vote of the Tory membership on a OMOV - one member one vote - system. Members need to have been paid up for three months to vote, and this part of the process will take longer.
The winner will become leader of the Conservative Party - and inherit the keys to Downing Street.
There would probably be considerable pressure at this point to outline plans for a general election.
A new leader would still have to grapple with Mrs May's wafer thin Commons majority - not a good platform for getting things done.
Could Theresa May survive a no confidence vote?
Opinion is split on how likely Theresa May would be to win.
For much of this year there had been a general consensus she would breeze through with ease.
There was even speculation that No 10 would move behind the scenes to help trigger a no confidence vote in order to get it off the table and consolidate the PM's authority.
But the twists and turns of the Brexit negotiations are damaging that sense of certainty. And there has been an uptick in negative chatter regarding her in the past few weeks.
Tory MPs will have to balance an opportunity to get rid of a leader many of whom consider deeply unpopular with the risk of worsening their party's fortunes.
Whatever the result, even triggering the process is a huge risk - it would threaten perceptions of stability and potentially give huge ground to opposition parties.
Many Tory MPs are also privately concerned about losing their seats if
such a process hastened an early election.
On the other hand, the growing groundswell of feeling that Theresa May's premiership is permanently impaired does not show signs of abating.