According to a new biography of the royal family, Prince William performed a choreographed dance to a medley from “Grease” at his wedding.

A new book about Catherine, Princess of Wales, reveals the secret of her wedding night, revealing that she and William danced to a medley of “Grease” before leaving the reception.

“Prince William and Kate had a special surprise in store for the finale of the evening,” wrote Robert Jobson in his new biography “Catherine, Princess of Wales.”

“They were standing in the middle of the dance floor, holding hands and grinning, when suddenly the first bars of the song You’re the One That I Want from the musical Grease rang out.”

Jobson, who serves as Royal Editor of the London Evening Standard, then described the couple’s choreographed wedding dance.

“William and Catherine then began dancing around, pointing at each other and mouthing the words in the style of the main characters Danny and Sandy,” he wrote.

“It brought the house down.”

The book also claims that it was William’s ex-girlfriend Carly Massy-Birch who first revealed the news of his previously secret romance with Catherine when all three were still students.

During the party game “Never Have I Ever,” in which players must name something they have never done, Carly reportedly said, “I have never dated two people in this room,” after which William confessed that he was actually dating Catherine.