Marian Duckworth Harbord was born in Looe. In 1911 the family were living in Coalbrookedale, Shropshire. At one point in her career, she worked in the Catskill Mountains in the USA. 

In 1939 Marian and her mother were living in 'Pounds Cross' just outside Polperro. Three of her artworks were included in the Polperro Art Society's 1939 show. In the same year her portrait of a child 'Joan' was shown at the Royal Academy, and she achieved further success there in 1941 with a portrait, 'Mary'. Her portrait of Herbert Morris was received with considerable acclaim.

In June 1941 she left Cornwall to work in the NAAFI. After her mother's death in 1945 she moved to London.