Marlborough House, Westminster, London, c1710 (1878). Marlborough House is a mansion in The Mall. It was designed by Sir Christopher Wren for Sarah Churchill, Duchess of Marlborough, a confidante of Queen Anne. For over a century it served as the London residence of the Dukes of Marlborough. It is now the headquarters of the Commonwealth Secretariat. From Old and New London Illustrated, Vol IV, by Edward Walford. [Cassell Petter & Galpin, London, Paris & New York, 1878]