LONDON — A year that has featured a triumphant Olympic Games and Queen Elizabeth II’s diamond jubilee struck an unwelcome bump on Wednesday for the royal family with the publication of photographs showing the queen’s sometimes wayward grandson, Prince Harry, naked and cavorting with a naked woman, or women, during a strip billiards game in a Las Vegas hotel room.

The photographs, on a Hollywood celebrity Web site, TMZ, were confirmed as genuine on Wednesday by aghast palace officials in London. The 27-year-old prince, whose boisterous ways are said to have alternately amused and infuriated his 86-year-old grandmother in the past, was reported to have flown back to London on Wednesday afternoon in a subdued mood, certain to face a family rebuke for slipping back into unprincely ways.

The incident was all the more jarring in a year that had otherwise gone so well for the royals. Crowds for the monarch’s 60th anniversary on the throne have been large, and jubilant. The queen’s popularity jumped when she played herself in the paradiving-with-James-Bond spoof that was part of the widely praised Olympics opening ceremony. Her granddaughter Zara Phillips, Harry’s cousin, won a silver medal as an equestrian.

Harry, son of Princess Diana and third in line to the British throne after Prince Charles and Prince William, mingled with athletes at the Olympics almost every day and represented the queen in the V.I.P. enclosure at the closing ceremony. He drew approving comments from British columnists, who said he appeared to have matured beyond his “wild days,” when he was regularly photographed in British newspapers tumbling, often visibly intoxicated, out of London’s priciest nightclubs.