LONDON, UNITED KINGDOM - DECEMBER 20: (EMBARGOED FOR PUBLICATION IN UK NEWSPAPERS UNTIL 48 HOURS AFTER CREATE DATE AND TIME) Prince William, Duke of Cambridge, Prince George of Cambridge and Prince Harry attend a Christmas lunch for members of the Royal Family hosted by Queen Elizabeth II at Buckingham Palace on December 20, 2016 in London, England. (Photo by Max Mumby/Indigo/Getty Images)

LONDON, UNITED KINGDOM - DECEMBER 20: (EMBARGOED FOR PUBLICATION IN UK NEWSPAPERS UNTIL 48 HOURS AFTER CREATE DATE AND TIME) Prince William, Duke of Cambridge, Prince George of Cambridge and Prince Harry attend a Christmas lunch for members of the Royal Family hosted by Queen Elizabeth II at Buckingham Palace on December 20, 2016 in London, England. (Photo by Max Mumby/Indigo/Getty Images)