Britain's coronavirus testing programme was in disarray on Friday after it emerged that 43,000 people who were probably infected were given the all clear, fuelling a spike in cases.
The UK Health Security Agency (UKHSA) was facing questions about how it missed the testing blunder, when it had been spotted more than a month ago by scientists and amateur data analysts.
NHS Test and Trace suspended testing operations at the Immensa Health Clinic laboratory, in Wolverhampton, on Friday, after it emerged that people had received negative PCR test results despite previously testing positive by lateral flow devices.
Experts warned the error would be likely to lead to tens of thousands more coronavirus cases, as well as more hospital admissions and deaths, because huge numbers did not self-isolate.
'It will lead to a spike in cases'
Dr Kit Yates, of the University of Bath’s department of mathematical sciences, said there had been a "concerted effort" among experts to highlight the "strange results" - but little had been done until recently.
"People have been gaslighted into thinking they haven’t got Covid and they have been going into schools and offices and potentially infecting tens of thousands of other people," he said.
"We should have been getting people to isolate but, without a PCR, you can't convince your boss you need to isolate. A PCR has been put on this pedestal and thought to be always better than lateral flow.
"It will lead to a spike in cases, and we’re already seeing that in places like Stroud. Currently we’re seeing rising cases in children, but that is now starting to bleed through to older age ranges - so this will impact on hospitalisations and deaths a few weeks down the line."
Crisis for UK Health Security Agency
The errors relate to test results given to people between September 8 and October 12, mainly in the South West of England, but with some cases in the South East and Wales.
In early September, scientists and data analysts pointed out that case numbers in the south west seemed artificially low, and noticed that unusually high numbers of positive lateral flow tests were coming back negative when checked against the gold-standard polymerase chain reaction (PCR).
The Office for National Statistics (ONS) infection survey had also recorded surging cases in the south west, even though it was not apparent from the Government's daily coronavirus dashboard.
It is the first crisis for the UKHSA, which has recently replaced Public Health England (PHE) after the organisation was criticised for its early handling of mass testing,
Jenny Harries, chief executive of the UKHSA, told the BBC that "feedback" and "queries" about testing issues had been coming through "over the last two or three weeks" from public health directors in the south west.
But she admitted it was only in the past few days that they had "dug right down" into the geography and discovered testing discrepancies.
She said it was "not clear yet" what went wrong in the private laboratory, adding that it was "accredited to all of the appropriate standards".
'Questions that need to be answered'
The Government awarded Immensa a £119 million contract in October 2020 to urgently "develop volume for PCR testing for Covid in line with test and trace requirements", the contract shows.
However, in January, an investigation by The Sun newspaper showed workers fighting, drinking alcohol, playing football and sleeping in the Wolverhampton lab.
Andrea Riposati, chief executive of Immensa, is also chief executive of Dante labs, which is under investigation by the Competition and Markets Authority (CMA) for issues including not delivering PCR tests or results on time.
Adam Finn, Professor of Paediatrics, University of Bristol and a member of the Joint Committee on Vaccination and Immunisation (JCVI), said that his team had flagged the issue to the director of public health in Bristol several weeks ago.
"This was not an invisible problem," he said. "A number of people have been puzzled by getting positive lateral flow tests and then getting negative PCR.
"This has been around for two or three weeks. We have been aware of it and warned about it. How did it take a month to notice? In my lab, we would notice immediately if there was a problem.
"There are questions that need to be answered. We need reassurance that it won’t happen again."
Error 'could have cost lives'
NHS Test and Trace is contacting people who could still be infectious to advise them to take another test, while close contacts who are symptomatic will also be advised to take a test, as is already recommended.
However, because of the delay, it was likely only a few thousand of the 43,000 affected were still infectious, Dr Harries said.
Tim Barton, 48, said he and his family received positive lateral flow tests after falling ill with coronavirus symptoms earlier this month, but their PCR tests came back negative.
Mr Barton, a client relationship director, said: "My son, daughter and myself all had positive lateral flow tests - we then had PCR tests done at the test site in Swindon all of which came back negative.
"This will undoubtedly impact people's confidence in the accuracy of these types of tests. They could have cost lives."
Graham Loader, from Newbury, also said his family had three positive lateral flow tests, all followed by negative PCR tests taken at the testing site at Newbury Showground, in West Berkshire.
His wife, a schoolteacher, returned to work after a negative PCR test.
Mr Loader, who coaches a boy's football team, said: "I completely trusted the PCR, so I feel bad for all the people I've been in contact with."
'Something wasn't right'
The issue was first noticed in early September, when scientists and data analysts on social media noticed that cases in the South West had started to plummet.
Local authorities that had been experiencing worrying hotspots, suddenly saw case rates drop to a tenth of the previous number in just a fortnight.
Experts said it was unusual, because such dramatic falls did not even happen in areas of self-limiting outbreaks, such as in factories or prisons.
Dave McNally, who was watching the data closely, pointed out the strange numbers on Twitter, posting a graph which showed that PCR testing had "pretty much halved" in the space of seven days between September 9 and September 16.
He told The Telegraph: "A few of us noticed on September 10 that something wasn’t right in the number from September 8.
"By September 20, it looked clear to me that PCR samples were going wrong in some way."
While the west of the country had been responsible for roughly six per cent of England’s daily case numbers since the start of August, overnight it dropped below three per cent during mid to late September.
Although case rates rose back to normal level towards the end of September, by the beginning of October the numbers were falling suspiciously again.
In early October, members of the public began to report that despite having symptoms of Covid and multiple positive lateral flow tests, they were still being told they did not have the virus.
Professor Adam Finn, Professor of Paediatrics at the University of Bristol, said: "We have a regular meeting to discuss the condition of the pandemic in Bristol every month," adding that it was "at least two weeks ago, if not more, that this was first brought up".
He said: "A number of people have been puzzled by getting positive lateral flow tests and then getting negative PCR. This has been around for two or three weeks. We have been aware of it and warned about it.
"The director of public health in Bristol knew about it. I would have expected that there would have been some communication about it. This was not an invisible problem."
It was around this time that news of a ‘super cold’ emerged, with people claiming to feel dreadful, yet testing negative for coronavirus.
When the social media analysts began looking at the test results more closely, they realised something very odd was happening.
Normally, because of the delay in PCR test data coming back from labs, the daily specimen count is revised up as more results are returned. It is usually completed five days later.
But in nine areas of the south west, the opposite was happening. The figures were being revised down.
What became clear was that large numbers of lateral flow positives were being removed from the figures.
Latest data from the infection survey shows that the south west is now one of the worst areas in the country for Covid cases, most likely driven by the cases that were not picked up.