Boris Johnson will hear the advice of his medical and scientific experts at a crunch meeting this evening, before deciding on what would be the third crackdown in little more than a week.
More areas of England – in the midlands and the north – seem certain to be moved into tier 4, with an instruction to stay at home and a limit of meeting only one other person outdoors.
But growing alarm over the rapid spread of the new, more infectious Covid variant has put ministers under pressure to introduce even harsher curbs in the capital and other areas of the south.
It is thought they could include banning people from leaving their homes for non-essential reasons – matching the restrictions at the outbreak of the pandemic, in March – although they are unlikely to be called tier 5 officially.
A Cabinet battle is still raging over whether to keep some schools closed in January, to curb transmission, with no decision expected today.
The prime minister has repeatedly failed to rule out a third national lockdown – something Andrew Hayward, of the government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), suggested might be necessary.
“We’re entering a new dangerous phase of the pandemic and we’re going to need decisive, early, national action to prevent a catastrophe in January and February,” Professor Hayward said.
“A 50 per cent increase in transmissibility means that the previous levels of restrictions that worked before won’t work now and so Tier 4 restrictions are likely to necessary or even higher than that.”
The Independent understands that the prime minister will host a meeting of the Covid committee that decides on the tier level in each area, in Downing Street on Tuesday evening.
On Tuesday, the prime minister’s spokesman did not deny that some of the Nightingale hospitals are not being used because of nursing shortages – despite more Covid patients on wards than the previous peak in April.
Asked about a report that the London Nightingale is being stripped of beds, he said only that it was “not my understanding that any have been dismantled”.
And he rebuffed pressure for teachers to be given early vaccinations, saying there would be no change to excluding them from the priority groups.
On the timing of school reopenings, the spokesman said: “We’re still planning for a staggered opening of schools and we are working to ensure testing is in place.
“As we have said throughout the pandemic, we obviously keep all measures under constant review.”