When he stood in front of the nation on Monday evening, Boris Johnson made clear his opposition to a new national lockdown plan, warning it would cause "immediate harm", and adding: "We don't want to go down that extreme route right now."
But, just 24 hours later, Mr Johnson's commitment to that pledge was being put to the test with Labour leader Sir Keir Starmer openly in favour of the 'circuit breaker' national lockdown, backed by the Prime Minister's own scientific advisers.
Mr Johnson will now come under pressure from the 'doves' in his Cabinet once again to subject the nation to stricter lockdown measures. For the 'hawks' in Mr Johnson's Cabinet, it was a battle they thought they had already won.
Cabinet ministers had been discussing for three weeks the guidance from the Sage group of scientific advisers which stated that what was needed was a national lockdown of several weeks to “put the epidemic back” by at least 28 days.
Yet on Monday Mr Johnson rejected this advice and backed a three tier system to divide England in "medium", "high" or "very high" risk areas, with an escalating degree of restrictions on social mixing.
In doing, so he was heeding the advice of Cabinet hawks like Rishi Sunak, the Chancellor, Robert Jenrick, the Housing Secretary, Alok Sharma, the Business secretary, and Oliver Dowden, the Culture secretary, who were desperate to keep as much of the economy open as possible.
But, soon after finishing his address to the nation, minutes from Sage meetings were published, warning that a failure to go further could result in "a very large epidemic with catastrophic consequences".
A two-week national circuit break lockdown to halt the virus had been first proposed on September 17 by one of Sage's subcommittees.
The scientists and health experts appeared to be preparing the ground for tougher restrictions at a meeting of the Cabinet Office's 'Covid-19 Operation' committee some two days later.
This Covid-O committee runs the Government's daily battle with coronavirus. Its official role is "to deliver the policy and operational response to Covid-19", according to the Government's website.
Officially, it has a standing membership of three: its chairman Michael Gove, the Cabinet Office minister, and Matt Hancock, the Health secretary (both seen as 'doves') and Mr Sunak, a solitary 'hawk'.
Crucially, other hawkish ministers are allowed to attend, including Mr Dowden, Mr Jenrick, Mr Sharma, as well as Priti Patel.
At the meeting on September 18, the hawks headed off the calls for the circuit break and recommended the three tiers plan. It was backed by Mr Gove and Mr Hancock.
Yet as ministers and officials then set about working out the thresholds for triggering communities moving into the different levels, pressure was still coming from the Government's scientists for a lockdown.
The fateful Sage meeting was held three days later on September 21, with Sir Patrick Vallance, the chief scientific officer, and Chris Whitty, the chief medical officer.
It agreed that “a package of interventions will need to be adopted” to reverse an exponential rise in cases, with latest data suggesting the doubling time for new infections could be as short as seven days.
As well as the circuit breaker lockdown, other ideas included banning all contact between households, and closing all pubs and restaurants, working from home, and banning all university face-to-face tuition.
That same evening, the Prime Minister addressed the nation urging people to work from home if possible, and to abide by a 10pm curfew for pubs, even though Sage thought would only have a “marginal impact” on the spread of the virus.
In the Cabinet, the hawks were pushing back against a circuit breaker lockdown. One source said the problem with a two-week circuit breaker was that it would merely delay rather than suppress a second wave of covid-19. "It doesn't break the circuit. It just delays things," said the insider.
Mr Hancock and Mr Gove continued to argue "for more restrictive measures" in the Covid-O committee, according to a senior source.
Yet the doves were pushing for a less restrictive baseline of measures which could be added to by local city and regional leaders, according to the specific characteristics of their areas.
Mr Dowden, Mr Jenrick, Mr Sunak and Mr Sharma backed an "approach that attempts to balance the obvious risk of Covid with the other damage we see being done to livelihoods, mental health, other conditions".
A senior source said: "Hancock and Gove were the only two that consistently advocate for the other approach."
Research by a Treasury economist Clare Lombardelli about the ruinous impact of a national lockdown also had a bearing on the Prime Minister.
A Cabinet source said the breakthrough "came through private discussions with the Prime Minister. Rishi has been excellent in making the argument consistently".
Mr Johnson came down in favour of the three tiers plan (with areas in England grouped as "medium", "high" or "very high", with additional measures agreed with local councils and mayors) when he recognised that the virus is likely to be around for many months, according to ministers.
The Cabinet source said: "You have to balance just looking at Covid-19 in isolation with the enormous damage that is being done to the economy, people's livelihoods.
"It was the realisation that we are going to be living with this for some time, and that a seriously detrimental blanket measure can only be temporary. If we are going to be living with this for some time, you have to take a more balanced view and that is what he is trying to do now."
The source added: "A blanket lockdown is incredibly destructive, and although things can change quickly, there is huge variety in cases of infection across the country."
Another Government source defended Mr Gove, saying: "Michael supported the tiering process. It was the Treasury and No 10 that came up with the idea that it would be locally led."
There was a false start to unveiling the plan last week, when ministers demanded a greater say in deciding which areas go into the higher tiers.
And even when Mr Johnson finally announced the three tier restrictions on Monday evening, Prof Whitty, standing alongside him was casting doubt on it.
“I am not confident, and nor is anybody confident, that the Tier 3 proposals for the highest rates, if we did the absolute base case, and nothing more, would be enough to get on top of it,” he said.
By Tuesday night, only the Liverpool city region had agreed to the new Tier 3 "very high" restrictions. Tuesday's talks with the regional leaders in Greater Manchester, Lancashire and the North East of England, led by Mr Johnson's chief strategic adviser Sir Edward Lister, were continuing.
An immediate agreement was said to be "some way off".
There was little doubt that scientists who had backed a circuit breaker were left frustrated. One adviser said: "We barely see our kids. We work late every night. So it does hit rather hard when your ideas get killed.
“Worst of all, they then impose restrictions like the pub curfew, which don’t appear to have any supporting scientific evidence at all. It’s a mess.”
Mr Sunak and the Cabinet hawks might have won the argument to avert a national lockdown. But for how long would their victory last? As one Government adviser said on Tuesday night: "It's time to hold your breath and see what happens."
Meanwhile, a coming study written by two leading Government scientific advisors will claim that between 3,000 and 107,000 deaths could be avoided if a circuit breaker lockdown is imposed over the October half-term.
Due for release on Wednesday, the paper, authored by Prof Graham Medley and Prof Matt Keeling, will claim that a circuit breaker would prevent between 5,000 and 140,000 hospitalisations by January, while limiting the “economic damage” of a lockdown.