From Buckingham Palace to 10 Downing Street, coronavirus knows no identity or station in life, however rarefied the individual. After Prince Charles, Boris Johnson (55) has tested positive and is “self-isolating” at home, indeed the world’s first head of government to be so afflicted.

Remarkably though, he has pledged to lead the government’s response to the accelerating outbreak, and from the sick bed as it were. “I’ve taken a test. That has come out positive,” Johnson said on Friday in a video statement broadcast on Twitter.

“I’ve developed mild symptoms of the coronavirus. That’s to say ~ a temperature and a persistent cough. So I am working from home. I’m self-isolating. Be in no doubt that I can continue, thanks to the wizardry of modern technology.” That resolute pledge, seemingly embedded in nerves of steel, is almost a defiance of the dreadful ailment.

Yet he has not evaded the primary function of any Prime Minister ~ to fulfil the Benthamite doctrine of the “greatest good of the greatest number”, verily that one’s work must do the talking. It was not immediately clear how many Downing Street staff and senior ministers would now need to isolate themselves given that recently many have had contact with Johnson.

His finance minister, Rishi Sunak, is not self-isolating, a Treasury source said. As Britons paid tribute to health workers on Thursday evening, clapping and cheering from doorways and windows. Johnson and Sunak took part, but came out of separate entrances on Downing Street and did not come into close contact.

The Queen last met Mr Johnson on March 11 and she remains in good health, Buckingham Palace said. Previously the government had said that Mr Johnson has the option to delegate to Foreign Secretary Dominic Raab, if needed. As it turns out, the Prime Minister is prepared to shoulder all responsibility so far as matters of state are concerned.

He was tested for coronavirus on the personal advice of Britain’s Chief Medical Officer, Professor Chris Whitty, a Downing Street spokesman said. At the time of writing, 759 people in the United Kingdom had died after testing positive for coronavirus and the number of confirmed cases had risen to 14.453.

The death toll is the seventh highest in the world, after Italy, Spain, China, Iran, France and the United States. Prince Charles, the 71-yearold heir to the British throne, tested positive for coronavirus earlier this week. He is in good health and is now self-isolating at his residence in Scotland with mild symptoms and is with his wife Camilla, who tested negative, his office said.

What Mr Johnson calls the “wizardry of modern technology and medical science” is on test not merely in Britain but the world over ~ from the migrant worker to the monarch.