The World Health Organisation's instructions were clear. "Our key message is: test, test, test," WHO head Tedros Adhanom Ghebreyesus said on March 16.
But while nations, including Germany and South Korea, have already tested hundreds of thousands of their citizens, Britain is lagging far behind, with the number of daily tests actually decreasing yesterday to 8240.
As ministers face growing questions over the failure to ramp up testing, the Daily Telegraph can disclose that officials have repeatedly ignored offers of help from many of the UK's leading scientific institutions.
Senior health sources also warned that the moment for Britain to launch a successful mass community testing programme may already have been lost.
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Professor Matthew Freeman, the head of Oxford University's Dunn School of Pathology, one of Britain's leading disease research institutions, revealed that his repeated offers to provide dozens of specialised machines and expert staff had been largely ignored by Public Health England.
He said the department had 119 of the crucial PCR machines used to identify tell-tale genetic signs of coronavirus, but health officials had accepted only one.
Hundreds of specialist workers and trained graduate students were on standby to help ramp up testing, he added, but despite initial signs of enthusiasm he had heard nothing more from PHE.
"We're clearly not doing as well as we could be doing as a nation when it comes to testing, and therefore people like us feel a bit frustrated," he said.
"I'm struggling to understand it. When they sent round a request a couple of weeks ago to supply the PCR machines, there was a very specific model they wanted. Of our machines, there was only one of that type, and the Army came and collected it and took it off to Milton Keynes.
"But we have another 118 that can broadly do the same job, but they don't appear to be part of PHE's plans. About two weeks ago, one of my colleagues spent two days trying to be a bit irritating and chasing PHE up to offer our help. They said, 'Oh that's great and we're really happy that you want to help'. Then nothing really came of it. That's the same for many institutions across the country. I can't understand why."
The Francis Crick Institute, a world-leading biomedical research centre based in London, has supplied five PCR machines to PHE so far, but is understood to have dozens more in its labs.
A spokesman said that no firm word had come from PHE as to whether any further machines or expertise would be required. "We have hundreds of scientists with different areas of expertise ready and willing to step in," the spokesman said. Other institutions across the country are understood to have had similar offers of help rejected by PHE.
Ministers are acutely aware that Britain's failure to carry out more tests has become the weak link in the response to the pandemic, and are desperate to ramp up mass testing.
Prime Minister Boris Johnson set a deadline of mid-April for testing to increase to 25,000 per day, only for PHE to say it could be the end of April before that target is reached.
There is also growing anger at the NHS's failure to take advantage of spare capacity in the system to test its own staff to get more back to work if they are virus-free.
Britain can now carry out 12,700 tests per day, but only 8240 tests were done in the 24 hours to yesterday, meaning opportunities were missed to test up to 4460 doctors, nurses and medical staff.
With up to a quarter of staff ill or self-isolating at some hospitals, Matt Hancock, the Health Secretary, made clear his frustration in a conference call with NHS and PHE bosses yesterday.
A rule that 85 per cent of tests had to be reserved for patients was scrapped by Hancock, who told hospitals there was now no limit on the number of staff tests.
Senior health sources, however, told the Daily Telegraph that the Government's strategy in the early stages of the pandemic may mean that Britain has already "missed the boat" on mass testing.
Initially Professor Chris Whitty, the Chief Medical Officer, and Sir Patrick Vallance, the Chief Scientific Adviser, decided with the agreement of senior ministers that the disease should be mitigated rather than suppressed, sources explained.
It was agreed that under the "herd immunity" approach, widespread testing would not be required as around 60 per cent of the population were expected to catch the disease anyway.
Instead, priority was given to protecting the vulnerable, and ensuring the NHS was not overwhelmed, by building up intensive care capacity, and procuring ventilators to keep patients alive.
That meant laboratory capacity was not increased, and there was no drive to order crucial components needed to produce testing kits.
On March 12, it was decided to halt community contact tracing, and to focus testing on hospital patients instead.
Other countries took a different path, and began buying up large stocks of kits for mass community testing.
Around two weeks ago, Britain's strategy switched after Imperial College modellers warned that leaving the disease to spread largely unchallenged could result in 250,000 deaths.
But by then, test kits were in short supply, and laboratories had not been readied for action. Initially, only a single government lab, PHE's main facility at Colindale, was charged with processing tests, with 11 more added later, along with 29 laboratory networks run by NHS Trusts.
At that stage, thousands of swabs sent to PHE by GPs who suspected their patients had contracted the disease were destroyed before being analysed because they did not meet strict criteria, sources revealed.
"If they had looked at those swabs earlier instead of throwing them away, we could have got a handle on this thing much earlier," one GP told this newspaper last night.
Laboratories are now struggling to buy in key chemicals needed to produce the testing kits, with reports that NHS Trusts have been forced to "home brew" their own.
At the Downing Street press conference, Michael Gove said: "The Prime Minister and the Health Secretary are working with companies worldwide to ensure that we get the material we need to increase tests of all kinds."
PHE officials now plan to launch "supercentres" to process the tests on a larger scale, in partnership with the private sector. A test centre for NHS workers opened yesterday in the car park of an Ikea store in Wembley, north-west London.
A PHE spokesman said: "Covid-19 only started to emerge at the beginning of the year and since then, PHE has managed to rapidly develop, validate and deliver an accurate test.
"PHE has since expanded to 12 other testing sites in England, and supported the NHS to start testing at greater capacity in their labs. This is the fastest deployment of a novel test to PHE and NHS labs in recent history, including in the Swine flu pandemic."