Prince William tested positive for the coronavirus in April, around the same time that his father Prince Charles tested positive.

British tabloid newspaper The Sun first reported that Prince William had kept his diagnosis private in order to not “alarm the nation.”

A source told The Sun: “At one stage he was struggling to breathe, so obviously everyone around him was pretty panicked.”

Kensington Palace, the home of Prince William, refused to comment officially, but palace sources confirmed to the BBC that the royal had contracted the disease.

Although the prince was hit hard by the virus, he still took 14 video and telephone calls in April. The Duke of Cambridge was treated by palace doctors and followed social distancing guidelines, quarantining himself for 14 days.

“After seeing medics and testing positive – which was obviously quite a shock given how fit and healthy he is – William was determined it should be business as usual though,” a source told The Sun.

The Duke was diagnosed days after his father The Prince of Wales and Prime Minister Boris Johnson had publicly come down with the disease. Sources said he kept his diagnosis private as the prime minister was treated in the hospital in order to not alarm the public any further.

“He felt there were more important things going on in the country,” the source said.

At the time, the Duchess of Cornwall, Prince Charles’ wife Camilla, had also gone into self-isolation for 14 days. Prince Charles, 71, said in and interview with Sky News in June that he was “lucky” and “got away with it quite lightly.”

This news of Prince William’s past diagnosis comes as England prepares to head into a four-week national lockdown starting on Thursday to curb the spread of coronavirus. The United Kingdom has seen more than 1,053,000 COVID-19 cases and 46,000 deaths as of Monday.