Marlborough House

Marlborough House, a Grade I listed mansion in St James's, City of Westminster, London, is the headquarters of the Commonwealth of Nations and the seat of the Commonwealth Secretariat. It was built for Sarah Churchill, Duchess of Marlborough, the favourite and confidante of Queen Anne. For over a century it served as the London residence of the Dukes of Marlborough. It became a royal residence through the 19th century and first half of the 20th. It was leased by Queen Elizabeth II to the Commonwealth beginning in 1965.