It was an admission that almost went unnoticed as Boris Johnson gave a press conference on the second lockdown on Thursday.
Asked whether he was concerned about the reliability of the data used to justify the month-long measures, the Prime Minister admitted: "Yes, the projections vary widely, the scientific estimates do vary widely, there’s no doubt about it.
"Some scientists take very different views from other scientists. That’s why you’ve got to add the political judgment that’s necessary about the economic consequences of what we are doing, the effect on livelihoods as well. You’ve got to factor all of these things in. It’s very, very tough to make exactly the right call."
Two graphs presented at a televised Downing Street press conference last week have since been amended after it emerged that separate modelling, showing a worst-case scenario of 4,000 deaths a day by the end of December, was based on out of date figures.
It came after the former Prime Minister Theresa May questioned the Government’s use of statistics to ask whether "figures are chosen to support the policy rather than the policy being based on the figures".
Now, contrary to suggestions that Mr Johnson was "bounced" into announcing the second lockdown after details of the plans were leaked prematurely, The Telegraph has learned that he had already made his mind up after the measure was discussed at the Friday Covid "quad" meeting.
Although Downing Street was planning to announce the new national restrictions in Parliament ahead of a press conference on Monday, claims the PM wanted to spend the weekend analysing further data now appear wide of the mark.
A well-placed insider said: "The decision was made by the Prime Minister on the Friday. The idea was to spend the weekend preparing for an announcement on the Monday – to brief Cabinet and avoid the party being taken by surprise.
"He was furious that the decision was leaked before he had the chance to make the case to Parliament – that’s why there’s a leak inquiry."
The three ministers at the "quad" meeting, chaired by the PM – Rishi Sunak, the Chancellor, Matt Hancock, the Health Secretary, and the Cabinet Office minister Michael Gove have all denied any knowledge of the leak.
Little wonder, then, that rebel Tories such as Mrs May appear to believe Number 10 is using the data to justify its political decision-making rather than the other way round.
As one veteran backbencher put it: "This is all about the pressure being exerted on Boris by [Dominic] Cummings and Gove. They’ve been wanting him to call a second lockdown since September, and if it wasn’t for Rishi that would have happened.
"They are absolutely obsessed with the death rate. They think that the only thing that matters, politically, is the NHS. And they convinced him it would be politically disastrous for him if he didn’t take that course."
Yet it seems Mr Johnson, a politician who cares deeply what others think of him, is also reluctant to be seen as someone wilfully putting lives at risk.
As the Tory MP Richard Drax told Chopper’s Politics podcast: "I suspect the fear of being accused, in the worst case, of being a murderer, which some people may aim at him if deaths continue to rise, is both for him morally and politically a very devastating accusation to make."
Such over-caution would certainly insulate Mr Johnson should he face such recriminations in a future public inquiry.
As the data relied upon by Number 10 comes under mounting scrutiny, pressure is building on Mr Johnson to establish a "red team" to challenge future coronavirus figures. Senior ministers and MPs are demanding that outside epidemiologists and experts be brought in to challenge the "robustness" of modelling provided by the Government’s scientific experts.
A minister said it was "absolutely right" that evidence used by the Government was subject to "wide and thorough debate", highlighting concerns that compliance with lockdown rules depended on people trusting the data.
Another Government source pointed out that Mr Johnson had previously invited other scientists into Downing Street to provide alternative arguments, adding that "red teaming" – bringing in outside groups to challenge group think – was regularly used across Whitehall.
The minister told The Telegraph: "There needs to be robust challenge. We’ve got the opportunity to use the next four weeks to regroup and come up with a longer-term strategy that takes people with us. We’ve got to make sure the data is as robust as possible."
A Cabinet source added: "There is a case for the ‘red team’, and the Cabinet would probably like a bit more of that. We need to have clarity of message but also have to accept that we are still learning about this virus everyday and that projections can change. We have to take people with us on this and air more of the considerations going on."
A third insider said: "Obviously it makes sense to scrutinise figures, and Sage members have been making that point as well as people in Government."
The disquiet in Cabinet has not gone unnoticed in No 10, with senior ministers on Friday night being invited to attend a data briefing early next week.