The black and white image shows a smiling Diana lying down on the lap of a young man who has just recently been identified as Adam Russell, a student at Oxford University at the time.
The words "Not to be published" are written across the photo. On the back, it is dated February 26th, 1981, two days after Diana's engagement to Prince Charles was announced.
The bidding starts at $200. The photo will be auctioned from January 17 to January 24.