If the world’s population isn’t fully vaccinated against Covid, new variants of the virus will continue to emerge.  It’s possible that, while our present vaccines and treatments can be adapted to counter dangerous ones, adaptation will take time (hopefully, only a few months).

Which would leave Ministers with three potential responses during this interim, as firms, governments and scientists scrambled worldwide to close down the problem.

First, a vaccine passport regime that restricts the freedoms of the unvaccinated – a course that David Gauke recommended yesterday on this site.  Second, lockdown-type state-imposed restrictions.  Third, relying on voluntarism and so increasing the risk to the NHS’ operability.

The question that the Government must grapple with is whether Omicron is such a variant, or whether it poses no real risk to the functioning of the health service.

Ministers and backbenchers could take a decision on the basis on the accuracy or otherwise of previous forecasts. Raghib Ali tweeted yesterday that “going back to the models, in general, actual outcomes have been much better than worst case scenarios and have been closer to the best case scenarios”.

In which case, a question follows: what if the SAGE that keeps crying wolf is right this time round?  If the precautionary principle applies, how precautionary should its application be?

For by the time MPs had key data that Raghib says they currently don’t – such as the case hospitalisation rate – it could well be too late for the Government to impose further restrictions that would significantly slow the spread of Omicron.

Raghib argues that our immunity is likely to be more robust than South Africa’s – and that what we know so far about the effectiveness of three vaccine doses suggests that the more pessimistic forecasts are wide of the mark.

Furthermore, he points out that the models don’t take into account voluntary changes of behaviour, which are clearly happening.  He therefore believes that the balance of the argument is against new restrictions. Which is where those rebels not opposed to these in principle were last week.

And where the majority of the Cabinet will have been yesterday.  Gone are the days when a quad of Boris Johnson, Rishi Sunak, Michael Gove and Matt Hancock could simply impose a view on their colleagues.  And another factor is at play.

Just as Liz Truss will come under scrutiny from backbenchers opposed to the Northern Ireland Protocol, so other Ministers, and Rishi Sunak in particular, will come under pressure from backbenchers suspicious of restrictions – plus a Spartan-style number of those opposed at almost any cost.

They will expect the Chancellor to be their champion and to deliver.  And he has indeed been particularly mindful of the needs of the economy during the long debate about how to deal with Covid, as one would expect.

But is is a statement of the obvious that the Prime Minister’s present position is weak, that he may be challenged in a confidence ballot, and that a leadership election may come in its wake.  In these circumstances, aspirant Tory leaders may act on the principle that “I am their leader so I must follow them”.

If having strong Ministers and weak backbenchers risks tyranny, not to put too fine a point on it, then having weak Ministers and strong backbenchers risks anarchy.

Raghib says that “the key metrics we need to predict are daily admissions/total number of patients and deaths, and how high they will go depends on the daily and total number of cases, and the case-hospitalisation rate, case-ICU rate and case-fatality rate”.

Johnson should call the Cabinet back before Christmas to have another look at the data as it continues to emerge.  That would usefully combine what he can get away with and should do in any event.