Blenheim Palace won the 25th-anniversary event, sponsored by the Historic Houses Association (HHA) and Christie's, last week. The award recognises the importance of gardens with outstanding horticultural and public appeal.
Christie's International deputy chairman Charles Cator said: "The vast park and gardens are immaculately kept with attention to every detail." HHA president Edward Harley added that Blenheim Palace owner the Duke of Marlborough showed "exemplary care, development and lifelong devotion".
Blenheim Palace, birthplace of Sir Winston Churchill, was designed in 1705 by Sir John Vanbrugh, who wanted to celebrate Britain's newly won supremacy over France with a rival to Versailles including 900ha of landscaped parkland and the formal gardens. Features include Italian gardens, water terraces, a rose garden and an arboretum.