The People has published images of the soon-to-be-married royal, who last month revelled in a low-key water-themed stag weekend, racing around in his boxer shorts at a friend's 21st birthday.
The images were allegedly taken in William's second year at the University of St Andrews, when the young Windsor's activities were subject to strict reporting restrictions.
A fellow partygoer said of the Prince: "He was cool about stripping off and really going for it. To think he's the future king of England is just incredible.
"He was having a boogie in his pants and a couple of feather boas.It shows how popular he was. Wills wasn't a big boozer - these were just high jinks."
