A failure in the official counting system has been blamed for Saturday's dramatic rise in reported Covid-19 cases across the UK.
The latest government data showed the number of confirmed cases of coronavirus had jumped by 12,872 in the 24 hours up to 9am on Saturday.
The figure of was s the highest daily rise since the pandemic began - though experts have warned against describing high totals as records because it is not clear how many people were actually infected during the height of the first wave.
Either way it was a sharp increase from the figures 24 hours earlier, when there had been 6,968.
Prime Minister Boris Johnson has now admitted: "The reason for that is because there was a failure in the counting system which has now been rectified."
He told BBC One’s Andrew Marr Show it was a "computing issue" and all those who had a positive test had been notified.
Quizzed on the issue earlier on Sunday, cabinet minister Brandon Lewis said: "I would say actually this is a testament to how focused the Department of Health, Public Health England, the Test and Trace are around the system.
"We are being transparent about this, we’re publishing the figures daily."
He told the Sophy Ridge programme: "As soon as they’ve spotted there was an issue, they’ve dug into that, they’ve got to the bottom of those numbers, they have been transparent and published the correct numbers and of course the teams will be looking through that to ensure it doesn’t happen again."
How were nearly 16,000 cases missed off the daily updates?
A "failure in the counting system" - now fixed - has been blamed for the dramatic rise in cases across Saturday and Sunday.
Public Health England (PHE) said its investigation into the issue with the government’s coronavirus dashboard identified 15,841 cases which were not included in daily reports between September 25 and October 2.
For example, 4,786 cases which were due to be reported on October 2 were not included in the daily total on the dashboard that day - when the figure was given as 6,968.
The issue was identified overnight on Friday 2 October.
Michael Brodie, the interim chief executive at Public Health England, said: "Every one of these cases received their Covid-19 test result as normal and all those who tested positive were advised to self-isolate.
"NHS Test and Trace and PHE have worked to quickly resolve the issue and transferred all outstanding cases immediately into the NHS Test and Trace contact tracing system".
Mr Brodie said "further robust measures have been put in place" to stop it happening again.
Test and Trace and PHE joint medical adviser, Susan Hopkins, said the issue had not prevented people receiving their test result and had not affected decision-making in local areas with regard to restrictions.
Here's how many cases were missed on each day:
957 cases on September 25, when the original figure given was 6,874
744 on September 26, when the original figure given was 6,042
757 on September 27, when the original figure given was 5,693
none on September 28, when the original figure given was 4,044
1,415 on September 29, when the original figure given was 7,143
3,049 on September 30, when the original figure given was 7,108
4,133 on October 1, when the original figure given was 6,914
4,786 on October 2, when the original figure given was 6,968
The government's official coronavirus dashboard said that due to a technical issue, which has now been resolved, there was a delay in publishing a number of cases.
It means Saturday's data, and that over the coming days, will include some additional cases from the period between September 24 and October 1.
Saturday’s figure brings the total number of cases in the UK to 480,017.
While a further 49 deaths were reported - bringing the UK total to 42,317.