Prince Harry was having his palm painted purple, so he could add his print to a wall display at the Turn Your Life Around Trust, according to Hello! The woman painting Harry's hand pointed to a spot on the wall where he could put his princely purple palm, but as she turned back to mischievous 30-year-old royal, she found he had dashed over to 74-year-old long-time royal photographer, Arthur Edwards, and planted a purple print right on the his forehead.

One of the event leaders is heard gasping in a video posted by Kensington Palace, "Oh my God, I can't believe you just did that!"

 A Prince and a prankster!