Some 20,000 former NHS staff have returned to the service to help in the fight against the coronavirus outbreak, Boris Johnson has revealed in a video as he self-isolates with the disease.

The prime minister thanked the doctors, nurses and other former medics for returning to duty, as well as the 750,000 members of the public who have volunteered to aid the health service.

Mr Johnson has continued to command the response to the Covid-19 pandemic while sealed behind closed doors in his flat above No 11 Downing Street.

In a video selfie, Mr Johnson said the public appeared to be obeying the terms of the lockdown to slow the spread of the disease, saying train use is down 95 per cent and buses down 75 per cent.

“Thank you to everybody who’s now coming back into the NHS in such huge numbers,” he continued.

“Just this evening I can tell you we have 20,000 NHS staff coming back to the colours.

“It’s a most amazing thing. And that’s in addition to the 750,000 members of the public who have volunteered to help us get through this crisis.”

On Thursday, NHS national medical director Professor Stephen Powis said the figure of former professionals who had volunteered to come back stood at more than 15,000.

Mr Johnson signed off his message with a contradiction of former Tory prime minister Margaret Thatcher’s endorsement of pure individualism when she declared that “there is no such thing as society”.

“We are going to do it, we are going to do it together. One thing I think the coronavirus crisis has already proved is that there really is such a thing as society,” Mr Johnson said.