Boris Johnson is facing the ever increasing prospect of a vote of no confidence from Tory MPs over the scandals surrounding lockdown parties in 10 Downing Street.
Reports suggest backbench MPs are edging closer to the threshold needed to trigger a vote, which could ultimately boot Mr Johnson from office.
It has been reported that an increasing number of the 2019 intake of Conservative MPs is behind a new push to oust the PM - who appeared to make his own situation worse yesterday with a cringeworthy interview on Sky News.
Read more: Boris Johnson to resign if he 'knowingly' he misled Parliament
If a no confidence vote happens it will be the second in just over three years.
Here we take a look at how the process may play out and what the rules are that could see Boris Johnson removed from office.
How many letters for a vote of no confidence?
Tory MPs trigger a no confidence vote in their leader at any time if 15% write to the chairman of the backbench 1922 Committee.
Currently there are 360 MPs with the Tory whip, so what means 54 of them need to send letters.
A letter is held on file by the '22 chairman until it is withdrawn by the MP who sent it. The chairman keeps a secret running tally of how many letters he has, and only makes an announcement if it tips over the 15% threshold.
Once a no confidence vote is triggered, a secret ballot is held of Tory MPs. Theresa May’s was held within hours.
If a no confidence vote succeeds, the Tory leader must resign and a full leadership contest is held.
But 50% of MPs need to vote “no confidence” for the motion to pass. Theresa May’s critics were undone by this in 2018, when they triggered a no confidence vote - but she then won it.
And once a Tory leader wins a no confidence vote by their party, they cannot be challenged again for a year.
Who is graham brady?
Sir Graham Brady is the long-serving Conservative MP for Altrincham and Sale West, a constituency he has represented since 1997.
But he is also the chairman of the very influential and currently critically important 1922 Committee of backbench Tory MPs.
It is Sir Graham that MPs will write to if they send those all important letters calling for Boris Johnson to resign.
If he receives the requisite 54 letters, we can expect Sir Graham to make an announcement that a no confidence vote will be held.
When could a no confidence vote take place in Boris Johnson?
If the 54 letters threshold is reached, precedent suggests the no confidence vote would take place very quickly.
Theresa May hit the threshold just before 8am and the vote was held that evening - it was all over by bedtime.
(If there is a full leadership contest, that would take a couple of months.)
So it all depends when the 54 letters threshold is reached. There’s feverish speculation that could happen in hours.
But others suggest most Tory MPs are still keeping their counsel until Sue Gray reports back on Partygate. That’s not expected until the tail end of this week, or next week.
Will a no confidence vote actually sack Boris Johnson?
It’s very hard to say. But we do know that it would need massive support to actually work.
While only 54 letters are needed to trigger a vote, half of MPs - 180 or so - would then need to vote no confidence.
The difference is that while people who send letters tend to become known, the election itself is a secret ballot. So some people will be more likely to call for the PM to go.
On the other hand, if a vote is forced before the Sue Gray report many Tories might sit on their hands.
One MP was downbeat. They told the Mirror: “I don’t know where it goes from here. We are grinding slowly to 54, but if we get 54 he will win the no confidence vote and notionally we can’t do it for another year.”
Who is in charge after the Prime Minister resigns or is sacked?
Leaving as Tory leader would not automatically remove Boris Johnson’s job as Prime Minister.
To resign as PM he must go to Buckingham Palace and offer his resignation to the Queen. He has a role in naming his successor, based on who can command the confidence of Parliament.
Importantly, he has some control over the timing of this.
Theresa May resigned as Tory leader in 2019 but remained as a ‘caretaker’ - or ‘lame duck’ - Prime Minister until her succession was chosen.
If Boris Johnson resigns as PM before a successor is chosen, the Cabinet Manual says it is “for the party or parties in government to identify who can be chosen as the successor”.
Who could the candidates be for Tory leader?
Chancellor Rishi Sunak and Foreign Secretary Liz Truss are the two names that come up most frequently in Westminster.
They have blatantly promoted their own personal brands, including with flattering photos by taxpayer-funded government PR photographers.
However, moderate Tories could try to stop right-winger Ms Truss getting on the ballot when MPs whittle downtime list.
