In the comedy sketch, Stephen Fry reprised his iconic role as Blackadder character Lord Melchett and was trying to help William with home schooling during the coronavirus lockdown.
As the time edged close to 8pm, Stephen gave William a 60-second warning ahead of the clapping, where the Duke joked he wasn't ready and had to get changed.
“On my way, let me just see if I can find my socks… and my shoes… and my trousers,” William quipped.
A few moments later, William, Kate and their three children, Prince George, six, Princess Charlotte, four, and birthday-boy Prince Louis, two, were seen outside their Anmer Hall home, where they are currently in lockdown.
Charlotte was the first to start clapping and was quickly joined by the rest of her family in the weekly tribute to the UK's care workers on the COVID-19 frontline.