KING Charles' infamous encounter with the Spice Girls will have gone some way to inspire Prince William's dad dancing at last week's Taylor Swift concert, says a royal expert.
Richard Fitzwilliams added that the Prince of Wales will not, however, be comparing himself to brother Prince Harry, who was spotted looking miserable 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 moves in a hip-hop style.
Later, he and children Prince George, 10, and Princess Charlotte, nine, posed for selfies with Swift, 34, herself and her boyfriend Travis Kelce, also 34.
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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.
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"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..."
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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.
"That's the key to it. Michelle Obama once said that Queen Elizabeth told her royal protocol was rubbish.
"Essentially, it's what the royals decide to do and what is acceptable."
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.
"I don't think William would take notice particularly regarding Harry, because there'd be no reason for him to," he said.
"I mean the two... they're very different people, as we know, and they have very different futures...
"No, no, I don't think that would be any problem there, and I don't think there would be any comparison."
Mr Fitzwilliams said Harry will essentially always be the "spare" but William must always be "looking to the future".
"Obviously, one day the monarchy that he takes over, when he is King, will be very different from that now.
"I mean always the institution has changed, and he realises that it's very, very important, and I think we've seen this in the appearances recently."
William was also seen in Germany watching England take on Denmark days before the Swift concert.
He has taken on more royal duties while Charles has been undergoing cancer treatment, while also dealing with the strains of wife Princess Kate's own chemo.
Asked what kind of monarchy William might look to see over when the time comes, Mr Fitzwilliams said: "Well, this is the big question.
"Of course, we're looking ahead, and it's very hard to be precise.
"He was once asked, would he be more the more activist King, or would he take a more conservative role?
"He indicated that he would take the Queen, late Queen Elizabeth as his role model."
Mr Fitzwilliams said occasionally William "speaks out" over certain issues and can be "quite the diplomat", including visits to Israel and Palestine.
"I think it is important to remember that he won't be coming becoming King tomorrow, and I can't speculate too far in advance, because the monarch is above party politics.
"You have to make that point. You also have to make the point that if you are the head of the forces, the church, the judiciary, the civil service is not the power you wield, it is the power you deny to others that won't change.
"His role is weekly audiences with the Prime Minister signing bills into law, opening Parliament, and so on."
He said "as far as idiosyncratic aspects" in a similar way to Charles championing environmental causes and religious understanding, "you expect William to prize mental health and so forth".
"These are very important topics, and he's done a lot for them. So expect certain themes to be developed...within the confines of the job, which are quite considerable."
Mr Fitzwilliams added: "In Charles, when Prince and Wales, was ahead of the game, in the sense that his then-Prince's trust, not the King's Trust, helped a million disadvantaged young people. That is a vast achievement.
"And he set up so many charities, which again is very significant, and of course we know, with architecture, homeopathy, and religious understanding. But he can be controversial.
"It is impossible to speculate on what sort of King William would be, but we have an idea if he's inspired by his grandmother, and also takes into account the superb [achievements] by his father."
