Prince of Wales check sports suit. Jacket by Scholte of London and stalking trousers (modified plus-fours) by Forster & Sons, 1923. Altered in the mid 1930s when a zip was inserted. Came with the removable blue cotton plus-four linings (more below)
While still not yet the King of England, David Windsor was regarded in America as the undisputed King of Fashion. The yellow-haired heir to the throne, variously known as the Prince of Wales and later as the Duke of Windsor, visited the United States in 1924 and made front-page news.
HM King Edward VIII (later Duke of Windsor) with his niece, Princess Elizabeth of York (later Queen Elizabeth II). The only photograph of just the two of them (that I've seen).