It's no secret that Prince William is a big Bon Jovi fan, having famously performed a karaoke cover of the band's hit Livin' On A Prayer at the wedding of his cousin Zara Phillips and Mike Tindall.
So the chance to sing the song alongside frontman Jon Bon Jovi was just too good to miss.
William stunned guests at the Winter Whites Gala on Tuesday evening by jumping up on stage with Jon and Taylor Swift for a spontaneous rendition of the track.
At the end of the night, the fun-loving Prince accepted an invitation to join the rock star for the performance, insisting he would only do it if Taylor came too. The trio then performed an acoustic version of Livin' on a Prayer in front of the 600 invitees.
The gala took place inside a specially-erected marquee in the grounds of Kensington Palace — where William now lives with wife Kate Middleton and their baby son, Prince George.
US star Taylor, who looked beautiful in a flowing cream and sequin gown, delighted the audience with renditions of her hit singles Trouble, Fifteen and Love Story.
"I'm Taylor, it is very nice to meet you, especially under these circumstances," she said as she arrived on stage. "It is my first time playing Kensington Place or any other palace for that matter.
"I have to thank you, Prince William, for having me. To call attention to this age group, especially teens and young adults.
"Taylor, 23, was clearly charmed by the down-to-earth royal. "He was funny," she later said of her initial introduction to the Prince at the champagne reception. "I was really happy he was funny."
Jon Bon Jovi, meanwhile, said that meeting William was far from an intimidating experience. "I met his father and I met his grandfather," said the musician, who was joined by his family at the gala.
"He's still a young kid to me, but a nice young kid.
"Guests including Eliza Doolittle, Downton Abbey actress Michelle Dockery, Colin Firth and his wife Livia Firth paid £500 each to attend The Winter Whites Gala, which was held in aid of Centrepoint, a charity for youth homelessness.
William has been patron of Centrepoint since 2005, following in the footsteps of his mother Princess Diana, who was a long standing and active supporter of the charity and herself became patron in 1992.
At the end of the concert, William took to the stage to present Jon with the Centrepoint Great Britain Youth Inspiration Award for his humanitarian work and make a heartfelt speech.
Referring to his fellow performers on the night, he couldn't resist joking that he "felt a duet with Tinie Tempah coming on", and said "that's not the first time James Blunt has sung and dedicated Your Beautiful to me".
But he stressed that despite the revelry, the evening was all about "those young people less fortunate than us, who, for reasons very often out of their own control, find themselves sleeping rough; not knowing where their next meal is coming from; without anyone to turn to; helpless.’