The UK has reported a record daily rise in confirmed coronavirus cases, with another 35,928 infections.
The update comes amid growing concern over a new variant of COVID-19 which appears to be causing a dramatic uptick in infections in London and the southeast of England, prompting the prime minister to enforce new Tier 4 restrictions.
Restrictions have also been increased in Wales and Scotland.
The new strain, which is up to 70% more transmissible, has been found in every part of the UK except Northern Ireland, an expert has told Sky News.
In England alone, 32,155 new cases were announced on Sunday, compared to 22,775 on Saturday.
Dr Yvonne Doyle, medical director at Public Health England, said the “sharp and sudden increase” in new cases on Sunday was of “serious concern”.
“Most of the new cases reported today are concentrated in London and the South East, although it is too early to tell if this is linked to the new variant,” she said.
“What we do know is that the way to control this virus is the same, whatever the variant. It simply will not spread if we avoid close contact with others.
“Wash your hands, wear a mask, keep your distance from others, and reduce your social contacts.
“By working together we have tackled this virus before. By holding the line over the next few weeks, it is possible we can do so again, as we continue to roll out the vaccine to the most vulnerable.”
Another 326 deaths within 28 days of a positive test were recorded across the UK on Sunday, taking the total number of coronavirus-related deaths to 67,401.
The number of cases now stands at 2,040,147.
The five-day Christmas bubble period has been reduced to just Christmas Day for England, Wales and Scotland – and scrapped completely for areas in England under new Tier 4 rules – but remains in Northern Ireland.