Sarah Churchill, Duchess of Marlborough
Ralph Montagu's position was further strengthened in 1705 by the marriage of his son and heir to Mary, daughter of John Churchill, 1st Duke of Marlborough and Sarah Churchill, Duchess of Marlborough. In the same year he was created Duke of Montagu and Marquess of Monthermer. His London residence, Montagu House, Bloomsbury, was bought by the government in 1753 to hold the national collection of antiquities, and on its site was built the British Museum.