Gladys Maude Winifred Mitchell was born on 19 April 1901 in Cowley, near Oxford, England, to James and Annie Julia Maude (Simmonds) Mitchell; her father was of Scottish background. She was educated at the Rothschild School in Brentford and the Green School in Isleworth; in Middlesex, where she had moved with her family in 1909; and at Goldsmith's College (1919-1921) and University College, London, where she qualified as a teacher and took a diploma in European history (1926).

During her long career Mitchell was not only a prolific writer but also a teacher of history and athletics and an athletic coach. After graduating from University College she taught at a small Anglican school, St. Paul's in Brentford, for over four years and then took a position at St. Ann's Senior Girls' School, Hanwell, where she remained until 1939. After a period of illness she became a teacher of Spanish as well as of...