The young royals joined their parents, the Duke and Duchess of Cambridge, for the BBC event which was held on the grounds of Buckingham Palace on Saturday 4 June.
Charlotte, seven, and George, eight, sat in the front row of the royal box between Prince William and Kate Middleton, clapping and waving small Union Jack flags.
As noted by social media users, they seemed particularly enthusiastic during Queen and Adam Lambert’s performance of “Don’t Stop Me Now” and Rod Stewart’s rendition of Neil Diamond’s “Sweet Caroline”.
“The most precious thing I’ve ever seen,” one Twitter user wrote. “Prince George knows the words – father and son singing along together like that. Happy tears.”
“How pleased was Princess Charlotte to see her Great Grandma with Paddington Bear!” one person wrote.
Another said: “Look at that excitement from Prince George and Princess Charlotte! Too Cute!”
Others praised Charlotte and George’s jubilee-themed outfits.
The event marked the children’s second public appearance of the day.
On Saturday afternoon, they joined their parents on a visit to Wales to meet performers and crew who took part in a Platinum Jubilee Celebration Concert at Cardiff Castle.
Charlotte delighted fans as she joined her mother and father in a playful attempt to conduct an orchestra.
Video footage showed William encouraging his daughter to try her hand at conducting as the orchestra began to play Lin-Manuel Miranda’s popular song, “We Don’t Talk About Bruno”, from Disney’s Encanto.
Charlotte was reluctant at first, but soon began waving her hands and the makeshift baton – which looked like a pencil – in the air.
The young princess was then seen smiling and giggling at her brother and father as she moved her hands.
On social media, fans said the video had brightened their day.
“Love when Princess Charlotte started to conduct the orchestra and she and Prince George laughs, the entire family is so adorable,” one person wrote on Twitter.
Another said: “Gotta give it to William, he was getting into the conductor spirit! Charlotte was so sweet and Kate did a good job too! George is just like, my parents are so embarrassing hahahaha… typical kid.”
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