Pincess Diana's 'mystery man' is no longer a mystery! The young man seen lounging with the royal in a candid 1970s photo that went up for auction on Friday was identified by Princess Di biographer Andrew Morton as a onetime Diana suitor who missed his chance.

"I was given the task of trying to identify the boy in the picture," Morton told The Guardian via email on Friday, after the photo caused a stir. "I later found out that the young man was Adam Russell, the great-grandson of former prime minister Stanley Baldwin, and now a deer farmer on Dorset."

Morton said the photo was taken on a ski trip during which Russell and Diana became close after they both suffered injuries and were forced to stay off the slopes.

"They kept each other company while the others went skiing and, at the end of the holiday, Adam was somewhat smitten," Morton told the British newspaper. "But absolutely nothing happened."

The pair stayed in touch after the trip, according to Morton, who says Russell hoped to start a romantic relationship with Diana but found he'd missed his window after spending a year traveling.

"When he arrived home a year later it was too late," Morton told The Guardian. "A friend told him, 'You've only got one rival — the Prince of Wales."

The never before seen photo snapped right before her engagement and capturing a carefree lifestyle she was days away from losing, is up for sale at a New Hampshire auction house. How a picture of the most photographed woman of her lifetime slipped by the public’s notice is a mystery, as is why the words “not to be published” were scrawled across the photo.

The picture was sold to a British newspaper on Feb. 26, 1981, which matches the date written on the back of the photograph. Two days before, Diana’s engagement to Prince Charles was announced by Buckingham Palace.

She was so gorgeous wasn't she.  I was obsessed with everything Diana from an early age.  She is dearly missed.

~Vanessa