Margaret Rule, née Martin, was born in High Wycombe, Buckinghamshire. She studied chemistry at the University of London, but later switched to studies of archaeology and helped to excavate bomb sites in London after World War II. In 1949 she married Arthur Rule, with whom she had a son, and later moved to Sussex. By 1960, she was serving on the local archaeological committee at Chichester, where she co-directed excavations with Alec Down.
Following the discovery of Roman remains in a field at Fishbourne, she and Barry Cunliffe began an excavation that revealed the Fishbourne Roman Palace. She became the first curator of the museum built at the site in 1968 by the Sussex Archaeological Society, and the author of Fishbourne Roman Palace (1977). She began her work in marine archaeology when she was consulted on the search for the wreck of the English warship Mary Rose, which sank in the Solent outside Portsmouth harbor in 1545. In 1967, with Alexander McKee, she established the Mary Rose Committee. Margaret learned to dive in order to help search the seabed
along with a team of volunteer divers exploring the area. The wreck was identified in 1971, and was the basis of her book The Mary Rose: The Excavation and Raising of Henry VIII’s Flagship (1982). Margaret was also instrumental in lobbying for the Protection of Wrecks Act in 1973, which designated the Mary Rose as the first protected historic shipwreck site. Her other notable projects included the excavation of a sunken Roman merchant ship in Guernsey, the subject of A Gallo-Roman Trading Vessel from Guernsey: The Excavation and Recovery of a Third Century Shipwreck (1993).