King Charles' infamous encounter with the Spice Girls may have inspired Prince William's dad dancing at last week's Taylor Swift concert, according to a royal expert.
Richard Fitzwilliams added that the Prince of Wales, however, would not be comparing himself to his brother Prince Harry, who was spotted looking downbeat at a Beyoncé gig.
William celebrated his 42nd birthday on June 21 at Wembley as the Shake It Off singer brought her Eras Tour to London. He was filmed by fellow concert-goers busting hip-hop moves.
Later, he and his children, Prince George, 10, and Princess Charlotte, nine, posed for selfies with Swift, 34, and her boyfriend, Travis Kelce, also 34. The snaps were then shared on the Wales' and Swift's official social media channels.
Mr Fitzwilliams told The Sun: "That is something that would never have been seen in the past.
"But equally, it's something that is very, very significant in the future, because social media is part of all of our lives, and he (William) knows that...
"There are echoes here, for example, of Prince Charles and the Spice Girls."
Charles - then the Prince of Wales - met the girl group in 1997, posing for photos.
Geri Halliwell broke royal protocol during the gala celebrating the 21st anniversary of the Prince's Trust, kissing Charles on the cheek and allegedly squeezing his bum.
"It's very significant that royals have to be seen to take note of current trends," said Mr Fitzwilliams.
"Not necessarily to be, so to speak, part of them in the sense that they won't be setting them, but to make sure that they're not behind them. I think that William's struck the right balance here."
He went on to say: "I think that the dad dancing clip wasn't necessarily one that he expected to be posted..."
The viral footage and selfies with Swift "remind us of how human the royals are".
"The royals can loosen up, but they can also be formal. It's the way they balance the two," Mr Fitzwilliams said.
In September last year Prince Harry was spotted alongside wife Meghan Markle at a Beyoncé gig in California looking downbeat, with many on social media labelling him "miserable".
However, Mr Fitzwilliams said it's unlikely William would have been trying to upstage his brother by appearing overly cheery at the Swift gig."