Britain initially took a restrained approach to the outbreak but changed tack after modelling showed a quarter of a million people in the country could perish.

Johnson imposed more stringent measures, effectively shuttering the world’s fifth largest economy, but the government has faced widespread criticism for having too few ventilators and too little testing.

“We’re also massively increasing testing,” Johnson said in a video message from a flat in Downing Street where he is self-isolating after testing positive himself.

“I want to say a special word about testing because it is so important. As I have said for weeks and weeks, this is the way through: this is how we will unlock the coronavirus puzzle, this is how we will defeat it in the end.”

Johnson’s message, posted on Twitter on Wednesday evening, followed pledges from his ministers to accelerate both antibody and antigen testing in the days ahead after a slew of sometimes contradictory statements on numbers already checked.

Antibody tests detect signs of an immune response while antigen tests detect whether the coronavirus is present.

While Germany has been testing about 500,000 people a week, Britain’s current capacity is about 13,000 a day, a figure the government said it was aiming to double by mid-April.

As of 0800 GMT on April 1, 152,979 people in the United Kingdom have been tested, of which 29,474 were confirmed positive. Deaths rose 31% to 2,352 as of 1600 GMT on March 31.

‘DEFEATING THE VIRUS’

Tests are essential for both fighting the virus and nursing the economy back to health after what is expected to be the worst quarter in around a century.

Testing frontline health staff allows those with immunity to return to work while broader testing of the population would allow tens of millions of idled workers back to work.

Showing just how bad coronavirus could be for the economy, British Airways said it was in talks about suspending 32,000 employees, while a survey showed that more than a quarter of British companies reduced staff levels.

So far, tests have been focused on those suspected to have the virus and admitted to hospital, but the government plans to increase testing of frontline healthcare staff to hundreds of thousands in coming weeks.

Ministers have suggested shortages of necessary chemicals were a factor, though the industry has said the necessary reagents are being manufactured and delivered to the National Health Service (NHS).

While the government has been forced on the defensive over mass testing, some scientists have questioned if testing the entire 1.1 million full-time NHS staff is the best use of resources.

Paul Nurse, chief executive of the Francis Crick Institute, a biomedical discovery institute researching the biology underlying human health, said Britain was not ready for the outbreak and for mass testing in particular.

“We weren’t sufficiently prepared, I think that’s clear but now the time is to get our shoulder behind the wheel and do as much as we can to help everybody in this country,” he told BBC radio.