WINDSOR, UNITED KINGDOM - MAY 15: (EMBARGOED FOR PUBLICATION IN UK NEWSPAPERS UNTIL 48 HOURS AFTER CREATE DATE AND TIME) Prince Philip, Duke of Edinburgh watches the Driving for the Disabled class as he attends day 2 of the Royal Windsor Horse Show at Home Park on May 15, 2014 in Windsor, England. (Photo by Max Mumby/Indigo/Getty Images)