Catherine, Princess of Wales says it is “extraordinary” how long she and Prince William have been together. The 40-year-old royal first met His Royal Highness, 40, at the University of St Andrew’s back in 2001 but the pair did not tie the knot until 2011 and she remarked how their children Prince George, nine, seven-year-old Princess Charlotte, and Prince Louis, four, are often surprised how “young” they look in old photographs, During her first engagement in Wales, Catherine was handed an old photo by a member of the public and remarked: “Oh my goodness, is that from our engagement? We always…