(FILE PHOTO) In this photo composite image a comparison has been made between, Left; SURREY, ENGLAND - DECEMBER 15: Kate Middleton, Prince William's girlfriend, attends the Sovereign's Parade at Sandhurst Military Academy to watch the passing-out parade on December 15, 2006 in Surrey, England. (Photo by Tim Graham Photo Library via Getty Images) and Right; SANDRINGHAM, UNITED KINGDOM - DECEMBER 25: Princess Diana At Sandringham On Christmas Day. The Princess Is Wearing A Red Coat And A Broad-brimmed Black Hat. She Is Carrying A Bouquet Of Flowers. (Photo by Tim Graham Picture Library/Getty Images). Kate Middleton will be celebrating her 26th Birthday on January 9, 2008.