How to close the big gap between coronavirus tests carried out and testing capacity?
The government's excuse for why it didn't engage in a comprehensive testing and tracking approach to contain Covid-19 after it started to spread throughout the community was that - unlike Germany and South Korea - it did not have sufficient numbers of labs to process the tests.
Well that excuse is almost exhausted, because testing capacity is increasing rapidly.
Take for example the new super lab being built in Cambridge by AstraZeneca (AZN) and GlaxoSmithKline, using equipment and technology made in the UK by Primer Design, the molecular diagnostics division of Novacyt.
AZN's chief executive Pascal Soriot tells me the tests will start any day now and that it will have the capacity to process 30,000 tests every day as soon as early May.
From a standing start just a couple of weeks ago, a huge new testing facility is close to completion.
However this expansion of capacity highlights a separate and highly important infrastructure deficiency - which is how to actually test with swabs all the people who would be deemed a priority to test, and then get the swabs to the labs.
Because, believe it or not, right now the problem is not that there isn't enough capacity to process the tests, even though that was the glaring problem last month.
The bigger problem now is actually testing all the healthcare and key workers - in the police, fire service and so on - who have been promised tests.
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The point is that the government, even without the new Cambridge lab, has increased testing capacity to 35,000 tests per day, thanks to the establishment of other new super labs, in Milton Keynes, Alderley Park and Glasgow - to meet the health secretary's target of 100,000 tests per day by the end of April.
But what is striking - and some would say of concern - is that the number of actual tests happening is almost 40% below that capacity: on Saturday, the latest day for which testing data is available, there were just 21,626 tests.
More than 20,000 tests is a vast improvement on the 5,000 tests per day being carried out just a few weeks ago, but nowhere near enough to underpin a policy of testing and contact tracing within the community (that approach widespread in Asia, where the virus has been better contained than in Europe, which involves testing everyone with symptoms and then putting into isolation all those with whom they've had contact in preceding days).
The ingenuity shown by public and private sectors to increase testing capacity is impressive and reassuring.
But for this ingenuity to translate into a system that could make a further dent in the spread of the virus, and even underpin an easing of restrictions on our basic freedoms and important modifications of the lockdown, requires many more tests to actually happen.