Fans of the British royal family were stunned to learn this week that Prince William secretly battled COVID-19 back in April. At the time, he reportedly kept it a secret that he had coronavirus so as not to alarm the people of the United Kingdom.

William reportedly caught COVID-19 after his father Prince Charles and the British Prime Minister Boris Johnson each tested positive for the virus. Palace doctors treated William throughout his illness, and he followed government guidelines by isolating at his family’s home Anmer Hall in Norfolk. Despite being ill with coronavirus, William still managed to take part in 14 telephone and video call engagements throughout the month of April.

“There were important things going on and I didn’t want to worry anyone,” William told one observer at an engagement.

That’s not to say that the royal’s battle with COVID-19 was easy, however.

“William was hit pretty hard by the virus – it really knocked him for six,” a source told The Sun. “At one stage he was struggling to breathe, so obviously everyone around him was pretty panicked. 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. He was determined to fulfill his engagements.”

After news broke that Charles and Johnson had tested positive for COVID-19, William feared that the U.K. would go into panic mode if it was reported that he had it as well.

“The Queen delivered her ‘We Will Meet Again’ address, and he just didn’t want to worry people,” the insider added. “He felt there were more important things going on in the country. But as a result of his own experiences, he realises absolutely anyone can catch this awful disease – and knows how imperative it is that we all take this second lockdown seriously.”

Thankfully, William, Charles, and Johnson were all able to overcome the coronavirus and they each appear to be healthy again at this time. Johnson’s case was the most serious, as he had to be rushed to the hospital at one point, but he was eventually able to beat COVID-19 just as the royals did.