It was shortly before 6pm on Wednesday when the tide decisively turned.
The prime minister had just addressed the 1922 Committee of Tory backbenchers in an attempt to rally the troops following the chaos which followed Kwasi Kwarteng’s mini-budget.
Of the many questions which were asked by MPs, only one was mildly supportive, while every criticism of the government was greeted with supportive banging of tables inside Committee Room 14.
“She was wooden, cardboard, lacking in empathy,” said one MP present.
Another added: “She was crap and the atmosphere was pretty flat in the room. Even the whips couldn’t be bothered getting people to ask supportive questions.”
A week ago, most Tory MPs - even those who did not support her leadership bid in the summer - were willing to give her more time to prove herself.
On Wednesday evening, however, that all changed. The question on most of their lips was when - and how - could they get rid of her.
“If you’d asked me two weeks ago how long she had, I’d have said till Easter,” one backbencher told HuffPost UK. “Last week I’d have given her till Christmas. Now I think she’ll be gone by the end of the month.”
One former minister said: “Things are just too bad now. She has to go.”
“The campaign for next May’s local elections starts in February, so she has to go before then - ideally by the end of the year.” a senior MP said.
Adding to the sense of panic among the Tory ranks are the opinion polls which are consistently giving Labour leads of up to 33 points.
One MP said: “It’s all about damage limitation now. Keeping the PM or getting rid of her could be the difference between us being left with 50 MPs or 200 MPs after the next election. That’s how serious - and urgent - the situation is.”
But while the majority of Tory MPs now believe Truss must go, the mechanism for removing her from Number 10 remains unclear.
At least 20 letters of no confidence in her leadership have now been submitted, although that is well short of the 54 needed to trigger a vote. And even if that threshold were met, the 1922 Committee rules state the PM cannot be challenged until she has been in post a year.
But one former cabinet minister said “the rules are always flexible when you make them yourselves”, suggesting they could be changed very easily to facilitate Truss’s departure.
One thing the rebels do agree on, however, is that the Tory membership must have no say in it this time round, even though the party rulebook demands it.
“They fucked it up the last time round so they can’t have any say this time,” one experienced MP told HuffPost UK.
Another MP said: “We can’t go back to the membership again because they vote for whoever tells them what they want to hear, not for reality.”
One theory gaining traction is that the candidates putting their names forward all agree that when they are whittled down to the final two, whoever is in second place stands aside in favour of the MP with the most support.
One senior figure even suggested that Boris Johnson should make a public statement urging MPs to throw their weight behind whichever candidate gets the most support, even if it is his arch-enemy, Rishi Sunak.
“He needs to tell them they must put the national interest ahead of their own self-interest,” they said.
Some believe Sunak - who lost to Truss in this summer’s leadership campaign - should form a “dream ticket” with Commons leader Penny Mordaunt, who also lost out to Truss.
But one Tory aide said: “Penny’s seen by many as having sold out by taking a job from Truss.”
In a last-ditch bid to save her premiership, Truss yesterday sacked Kwasi Kwarteng and announced that she was reversing the plan to freeze corporation tax at 19p, rather than allowing it to increase to 25p.
But her faltering performance at the Downing Street press conference confirming the volte face only reaffirmed her colleagues’ suspicions that she is simply not up to the job.
One MP told HuffPost UK it was “dire”, while another said it was “dreadful”.
“How she thinks doing all these U-turns and sacking the chancellor doesn’t signify the end for her is beyond me,” one ex-minister said.
Truss does still have her supporters, but they are a rapidly dwindling band.
Paul Bristow, the MP for Peterborough, tweeted: “Some of the same colleagues (usually in safe seats) who ousted Boris Johnson, have openly undermined his successor since day 1. This is selfish and self-seeking. What do they want? They don’t deserve to be Conservative MPs. Plenty of talent on our candidates list.”
And former cabinet minister Nadine Dorries - who backed Truss’s leadership bid but has been critical of her since then - said those wanting her out were guilty of “a plot not to remove a PM but to overturn democracy”
But one former minister observed: “Boris famously said ‘when the herd moves, it moves’ when he was kicked out. Paul Bristow’s solution seems to be just slaughter the herd. It’s madness.”
While Truss still has a small chance of survival, the events of the last 72 hours, and the shift in mood among Tory MPs, have all-but extinguished it.
It now seems only a matter of time before the UK - unbelievably - has its third prime minister of 2022.