Gladys Maude Winifred Mitchell was born on April 19, 1901, in the village of Cowley, Oxfordshire, the daughter of James Mitchell and Annie Julia Maude Simmonds Mitchell. After attending Goldsmith’s College, University of London, from 1919 to 1921, from which she received a diploma in history in 1926, she became an elementary teacher, a career that lasted for more than a quarter of a century. Although she first began teaching out of financial necessity, her foray into the field of detective fiction in 1929 soon made her financially independent. During and after World War II she continued to teach because of the national teacher shortage.
Conservative in political philosophy, agnostic in her religious beliefs, Mitchell pursued her career as an educator until 1961; at the same time, she produced at least one mystery novel every year, writing under her own name and the pseudonyms of Stephen Hockaby and Malcolm Torrie. She was a member of the Society of Authors, the Crime Writers’ Association, and the Detection Club. She was also a fellow of the Ancient Monuments Society. In 1976 she was awarded a special award from the Crime Writers’ Association in recognition of her having written more than fifty mysteries. She died at her home in Dorsetshire on July 27, 1983, at the age of eighty-two. She was still writing mysteries at the time of her death.