The Prince of Wales has become the highest profile coronavirus case in the country, after Clarence House said he had tested positive for the virus.
Charles (71) is displaying "mild symptoms" of the Covid-19 illness but is in good health and spirits as he self-isolates at Birkhall in Scotland, a spokesman said.
A source added "medical advice is that it is unlikely to escalate into a more serious case".
The Duchess of Cornwall (72), who is also at Birkhall, in Aberdeenshire, has tested negative for the virus, so is separating herself from the prince.
The couple were tested by the NHS in Aberdeenshire on Monday, but SNP politician Joan McAlpine, a Member of the Scottish Parliament, raised questions about procedures, citing a relative with an underlying health condition who was refused a test.
Charles' office Clarence House said the prince and duchess were tested on the NHS as "they met the criteria required for testing".
Charles fell ill over the weekend and a source said his doctor's most conservative estimate was that he was contagious on March 13. Charles last saw the Queen the day before this date, at a private meeting at Buckingham Palace which was not attended by the Duke of Edinburgh, who at the time was thought to be at Sandringham.
Buckingham Palace said the Queen (93), who is staying at Windsor Castle with Philip (98), remains in good health and is following all appropriate advice.
The royal family's official Twitter account released an image of the Queen in her Berkshire royal residence yesterday evening holding her weekly audience with Prime Minister Boris Johnson on the telephone. The monarch was pictured using an old fashioned phone in a sitting room, adorned with ornaments including a china corgi.
Later, the official royal family Twitter account posted a tribute to all the volunteers helping to combat coronavirus.
"Volunteers always have a huge role to play in society, but never more so than in difficult times - and for that we salute you," it said.
It is not known when Charles was last in contact with the Duke and Duchess of Cambridge, and Prince George, Princess Charlotte and Prince Louis.
Clarence House said: "The Prince of Wales has tested positive for coronavirus. He has been displaying mild symptoms but otherwise remains in good health and has been working from home throughout the last few days as usual. In accordance with Government and medical advice, the prince and the duchess are now self-isolating at home in Scotland. The tests were carried out by the NHS in Aberdeenshire where they met the criteria required for testing."
Charles and Camilla are both over 70, the age group told to take social distancing particularly seriously.
Prince Albert of Monaco, who tested positive for the virus last week, sat opposite Charles for more than half an hour during a event held by the charity WaterAid on March 10 in London.