Mary Duncan studied at the Bromley School of Art and carried on her artistic education at the Slade School in London and then in Paris. Duncan moved to Dublin c.1910 and became good friends with Irish artist Estella Solomons. The pair would go on to exhibit together throughout their artistic careers, both moving within the literary and artistic circle of Dublin when she would have met Jack. During the 1920s Duncan exhibited frequently at the RSA, RA, and primarily at the RHA. In 1922 she returned to England and opened a studio for a short while at Bushey, Hertfordshire before moving to Cornwall in 1927, where she remained for the rest of her life. She continued to exhibit in Dublin, Edinburgh and London until 1953.