Video report by ITV News Correspondent Sejal Karia
The NHS will be "unable to cope" if Covid-19 cases continue to increase at the current rate, one of the country's leading scientists has warned.
The dire warning comes as millions more people across the country enter stricter coronavirus restrictions - with Wales moving into a national "fire-break" lockdown and South Yorkshire waking up to Tier 3 measures.
Professor Neil Ferguson warned rising infection rates could see the health system "unable to cope" while schools could be forced to close to some pupils.
Prof Ferguson, whose modelling led to the original lockdown in March, told the BBC Radio 4 Today programme: "If the rate of growth continues as it is, it means that in a month’s time we will above that peak level in March and that is probably unsustainable.
"We are in a critical time right now. The health system will not be able to cope with this rate of growth for much longer."
The epidemiologist said that though infections among 18 to 21-year-olds were falling, they were continuing to rise in other age groups.
He added: "There are little hints of slowing, for instance in the North East of England, but we are not seeing the sort of slowing that we really need to to get on top of this".
Prof Ferguson warned that if restrictions on households mixing fail to stem the rise of infections the government may have to close schools to older pupils.
"If we go beyond that there is a limit to what we can do in terms of reducing contacts, short of starting to target, for instance, the older years in schools and sixth form colleges where we know older teenagers are able to transmit as adults."
"Of course nobody wants to start moving to virtual education and closing schools even partially. The challenge may be that we are not able to get on top of the transmission otherwise."
His comments come as the number of people living under England's strictest Covid alert level increased by more than a million people - with South Yorkshire entering Tier 3 restrictions.
The region joined Liverpool City Region, Greater Manchester and Lancashire on the highest alert level with the new rules kicking in on Saturday at 12.01am.
It comes as talks were continuing between the government and local leaders in Nottinghamshire - with parts of the county expected to enter Tier 3 on Wednesday.
And the council in Warrington in Cheshire – where many residents commute to Manchester and Liverpool – has confirmed that it will be moving to Tier 3 on Thursday.
It means households will be banned from mixing except in parks and other open spaces while pubs and bars will have to close unless they serve meals.
Three more areas – Coventry, Stoke and Slough – have now also moved into Tier 2, the second highest alert level.
Elsewhere, Wales began a two-week national “firebreak” at 6pm on Friday evening with a return to the “stay at home” message of the initial lockdown in March.
In Scotland, First Minister Nicola Sturgeon has set out a five-tier series of controls which will come into force on November 2 if they are approved next week by the Holyrood Parliament.
Covid tiers: - What are the differences between each alert level in England?
Medium (Tier 1) - Rule of six applies indoors and outdoors. Pubs and restaurants close at 10pm.
High (Tier 2) - Households must not mix indoors in any setting including pubs and restaurants. Rule of six applies outdoors
Very high (Tier 3) - Households must not mix indoors, or in private gardens. Rule of six applies in outdoor spaces including parks. Pubs and bars which don't serve meals will be closed
In England, ministers have said they hope the latest measures will suppress the virus sufficiently to enable families to spend Christmas together.
Though some scientists advising the government remain highly sceptical, warning much tighter controls will be needed to get the situation under control and prevent many more deaths.
Speaking to the Today programme, Prof Ferguson said it will be a "political judgment" whether restrictions on households mixing should be relaxed over Christmas.
"It risks some transmission and there will be consequences of that. Some people will die because of getting infected on that day," he told the Today programme.
"But if it is only one or two days the impact is likely to be limited. So that is really a political judgment about the cost versus the benefits."
The latest figures suggest the number of new daily cases across England doubled in a fortnight – although scientists said the rate of spread of the virus may be slowing.
The Office for National Statistics (ONS) infection survey estimated there was an average of 35,200 new cases per day of Covid-19 in the community in England between October 10 and 16.
That was up 26% from an estimated 27,900 new cases per day for the period from October 2 to 8 and just over double the 17,200 new cases per day from September 25 to October 1.
The Scientific Advisory Group for Emergencies (Sage) said the reproduction number, or R value, for the whole of the UK had nudged down to between 1.2 and 1.4. Last week it put the figure at between 1.3 and 1.5.
A further 224 people had died within 28 days of testing positive for Covid-19 as of Friday, while as of 9am there had been a further 20,530 lab-confirmed cases in the UK.