King ' s lodge keeper who makes 64 kinds of wine at Windsor Castle flower show , private grounds open to public . By permission of the King , the entirely private part of the grounds of Windsor Castle were used for the 42nd annual rose and flower exhibition of the Windsor , Eton and District Agricultural Society . the King , an enthusiastic amateur gardner , is the society ' s patron . This is the only day of the year when this part of the grounds us open to the public . The king has given a challenge cup for sweet peas . Photo shows , competitors passing the South Western Lodge of Windsor Castle as they arrived with flowers . The Lodge Keeper is Mr W G Hearn . 11 July 1936