Educated at Heathfield in England and Sorbonne University in Paris,  Mary has had a long association with the Oppenheimer Memorial Trust, initially in the role of secretary in the 1970s and as chair of the Board of Trustees from 2001 to 2013. She resumed the chairmanship in October 2018.

An early interest in the arts resulted in board positions at Dorkay House, the African Music and Drama Academy and the Federated Union of Black Arts and she also played an important role as Managing Trustee of the Market Theatre from 1989 to 1992. Mary was instrumental in the founding of Business and Arts South Africa (BASA) in 1997 and served as its first chair. Established as a joint initiative of government and business, BASA set out to secure the development of the arts through increased corporate sector involvement and it has achieved many successes over the years.

Mary was one of the co-founders of Wiphold (the first female-controlled company to list on the JSE) and previously served as a Trustee of a range of other organisations including the Johannesburg Art Gallery, the Palaeontological Scientific Trust, the Contemporary African Music & Arts Archive, the Mali Manuscripts Trust and the World Wildlife Foundation and has an on-going interest in the work of the Caine Prize and the Helen Suzman Foundation.

Over and above her involvement with the OMT, Mary presently chairs The Brenthurst Library and Press.