Born Frideswide Frances Emma Stewart, and known as Frida, she was the daughter of Hugh Fraser Stewart (1863–1948) and his wife Jessie Graham Crum; her sister Caitin (Katherine) married George Derwent Thomson, and her brother Ludovic married Alice Mary Naish.
[7] Stewart then joined the Left Book Club and Communist Party of Great Britain, and formed local Spanish Aid committees on the outbreak of the Spanish Civil War.
[5][6] She drove an ambulance to Spain on behalf of the National Joint Committee for Spanish Relief.
[9] Arrested in France in 1940, after the German invasion, Stewart was in the Caserne Vauban (Besançon) and then the Vittel internment camp.
[18] She married microbiologist Bert Cyril James Gabriel Knight in 1944 and had five children, of whom four survived infancy.