Britain reported 1,325 new deaths from COVID-19 on Friday, its highest daily figure since the outbreak of the pandemic, with another 68,053 additional cases.
The total eclipsed the previous record number of deaths reported on April 21, 2020, of 1,224.
England entered a new lockdown this week with a "stay at home" message, as health officials cited rising hospital admissions that threaten to overrun the National Health Service (NHS).
London declared a major incident on Friday because its hospitals were at risk of being overwhelmed by a highly transmissible variant of the coronavirus racing "out of control" across the United Kingdom.
"Each life lost to this virus is a tragedy, but sadly we can expect the death toll to continue to rise until we stop the spread," said Dr William Welfare, Director for the COVID-19 response at Public Health England.
"To protect our loved ones it is essential we all stay at home where possible. This will reduce new infections, ease the pressure on the NHS and save lives."
(Reporting by Michael Holden and Alistair Smout)
