Just-Discovered Photo of Princess Diana and Mystery Man Goes On Auction

Mystery is swirling today over this newly discovered photo of the late Princess Diana.

Among the big questions: Who's the guy she's with? And who wrote "not to be published" on the picture?

The picture shows a beautiful, teenage Diana relaxing on a ski vacation, apparently in Switzerland. A hunky guy is cuddled up with her, reading a book and wearing a sweater that says "Ski Bob." Notice the bottle of Johnnie Walker whiskey sitting on the window ledge.

Most intriguing of all; that instruction "Not to be Published," which is underlined twice for emphasis.

On the back, the picture is labeled "Lady Diana," and dated February 26, 1981, two days after her engagement to Prince Charles was announced.

Although the photo was taken long before, there is speculation that Buckingham Palace, still giddy over the engagement, persuaded the newspaper which owned the photo to not print it.

Victoria Arbiter, ABC News' Royal Contributor told INSIDE EDITION, "Really, I suppose the thinking behind not publishing the photograph was simply that Diana had just become engaged to the future heir to the throne. She was going to be the country's future queen. So, to be seen possibly linked to an unidentified man may have added a hint of scandal."

And just who is the young man Diana is cuddling with?

"Chances are, he's just a good friend. They would have been on holiday with a group of people and he happened to be the person snapped with her at that moment," said Arbiter.

The photo is due to be sold by RR Auction later this month.