Rare Photo of Teen Princess Diana up for Auction

Entertainment Tonight, Friday, January 4, 2013, 6:44pm (PST)

Entertainment Tonight.

A never-before-seen photograph featuring the late Princess Diana has been made public in the weeks before the rare pic is set to go up for auction.

The black-and-white snapshot displaying a "not to be published" marking shows a teenage Diana lounging next to an until-now mystery pal, reportedly dating back to 1980.

Pics: Remembering Diana 15 Years After Her Death

"The young man was Adam Russell, the great-grandson of former prime minister Stanley Baldwin," Andrew Morton, Diana's biographer, revealed to the U.K.'s Guardian. Through his investigation, the writer discovered the context of the photograph was not intimate, as it appears at first glance. Apparently the twosome had been injured while skiing and simply kept each other company for the afternoon.

Now that's not to say the young man didn't escape Diana's charms.

Related: Naomi Watts Talks Princess Diana Movie - Exclusive

"Adam was somewhat smitten," adds Morton. "But absolutely nothing happened."

Related stories on ETonline.com:Exclusive: Jimmy Saves Regis From Gameday Freakout

Foxx: When I Knew I Was Famous