Britain's Catherine, Duchess of Cambridge (C) smiles as she arrives with Belgian Countess and wife of Hereditary Grand-Duke of Luxembourg  Stephanie de Lannoy (2L) during the Celebration of the 150th anniversary of the 1867 Treaty of London in Luxembourg, on May 11, 2017.  / AFP PHOTO / JOHN THYS        (Photo credit should read JOHN THYS/AFP/Getty Images)