She was a doctoral student of biochemist Hans Krebs, and was a fellow at St. Hilda's College, Oxford from 1971 to 2006.
[5] Mellanby worked on tetanospasmin and botulinum toxins as a postdoctoral research associate at Sir William Dunn School of Pathology.
In 1970, she and Larry Weiskrantz founded the Neurochemistry unit in Oxford's Experimental Psychology department.
She took a particular interest in secondary education and served as a governor of a local comprehensive school.
She helped to develop the VESPARCH test for evaluating verbal and spatial reasoning skills in students, as director of the Oxford Group For Children's Potential.