A British newspaper has identified the man in a controversial photo with a teenage Diana Spencer before she became Princess of Wales.
"The mystery man pictured with an 18-year-old Lady Diana Spencer has been unmasked as aristocrat Adam Russell," The Daily Mail said.
"Old Etonian Mr Russell, the great-grandson of former Tory prime minister Stanley Baldwin, is shown relaxing with the future Princess of Wales during a group ski holiday in Val Claret in the French Alps in 1979."
The photo was marked "not to be published" and showed Diana with a young friend seated beside her.
It will be featured in an auction this month in New Hampshire.
The photograph might never have been seen publicly until now, RR Auction said.
Stamped February 1981 on the back, the photo was taken around the time Charles, the Prince of Wales, and Lady Diana Spencer ended months of speculation and announced they were to be married.
The photo came from the Caren Archive, a major private collection of rare newspapers and other publications, and was purchased seven years ago from the Daily Mirror newspaper.
Bobby Livingston, vice-president of RR Auction, said on Saturday that neither the auction house nor Caren Archive knew the identity of the young man in the photo. However, he said he understood that a British newspaper had been able to identify him.
In 1981, Diana first told news of her engagement to her friends, then moved out of her apartment on February 23 and into Buckingham Palace.
What was widely labelled the wedding of the century took place on July 29, 1981, at St Paul's Cathedral in London.
Charles' and Diana's marriage ended in divorce in 1996, and Diana died in a Paris car crash in 1997.
Another Diana photo to be included in the auction is an original 1988 news photo of the princess observing a marriage conflict resolution seminar.
The auction is scheduled for January 17-24 in Amherst.