LONDON, UNITED KINGDOM - MAY 04: (EMBARGOED FOR PUBLICATION IN UK NEWSPAPERS UNTIL 48 HOURS AFTER CREATE DATE AND TIME) Catherine, Duchess of Cambridge visits the 'Vogue 100: A Century of Style' exhibition at the National Portrait Gallery on May 4, 2016 in London, England. The Duchess appears on the cover of the centenary issue in June 2016. (Photo by Max Mumby/Indigo/Getty Images)