Prince William and Kate Middleton appeared in a rare joint interview on Friday. The couple praised the staff and volunteers who are on the frontline during the COVID-19 pandemic. They highlighted the importance of mental health and wellbeing in this health crisis that has gripped the world.

The Duke and Duchess of Cambridge via video call from their country home in Norfolk, Anmer Hall appeared on the "BBC Breakfast" show on Friday.

During the chat, Prince William opened up about how he felt when his father, Prince Charles tested positive for COVID-19.

"I have to admit at first I was quite concerned. He fits the profile of somebody at the age he's at, which is, you know, fairly risky. And so I was a little bit worried. But my father has had many chest infections, colds, things like that over the years. And so, I thought to myself, If anybody is going to be able to beat this, it's going to be him," the 37-year-old royal.

The prince was thankful that his father only suffered mild symptoms, but the isolation was frustrating for him. "I think the hardest thing he found was having to stop and not being able to go and get a bit of fresh air and go for a walk. He's a mad walker, just loves his walking, so I think he found it quite difficult. Especially, I think also with his mental health, being stuck inside and not being able to go for walks," William added.

William and Kate are home-schooling Prince George, six, and Princess Charlotte, four through their spring break. Their school St Thomas's Battersea in London has been closed due to the coronavirus pandemic since March. The classes have moved online.

"Don't tell the children but we've actually kept it going through the holidays. I feel very mean," Kate, 38, told the BBC. The duke admitted that home schooling was fun while the duchess spoke about their little ones' "stamina."

"I don't know how they get it done honestly. You sort of pitch a tent, take the tent down again, cook, bake [and] you get to the end of the day. They've had a lovely time, but it's amazing how much they can cram into a day, that's for sure," Kate added.

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Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge arrive for their visit to Coventry Cathedral Getty

The parents-of-three revealed that they are being open with their brood about the pandemic. "George is much older than Louis is, but they are aware. I think I'm always surprised. Although you don't want to scare them and make it too overwhelming, I think it is appropriate to acknowledge it in simple ways and age-appropriate ways," the duchess said.