This photo of a young Diana Spencer - soon before becoming Princess Diana - is to go under the hammer at an upcoming U.S. auction.<br/> <br />The candid snap shows the princess-to-be smiling for the camera alongside an unidentified young man.<br/> <br />The photo originally came from the library of Britain's Daily Mirror tabloid newspaper.<br/> <br />Scrawled onto the photograph itself the are the words "Not to be published"<br/> <br />On the back, the photo is dated February 26, 1981 -- two days after Buckingham Palace announced her engagement to Prince Charles.<br/> <br />The mother of the second in line to the throne, Prince William, died in a Paris car crash in August 1997, a year after her divorce from Charles.
