Mitchell was born in Devon and educated at Torquay Boys' Grammar School and University College London from which he graduated with a BA in French and Spanish in 1940.
He then served with the Royal Artillery of the British Army in India, Burma and the Middle East until discharged as a Major in 1946.
[1] Mitchell's first academic appointment in 1946 was at the School of Oriental and African Studies (SOAS) in London where he worked with Professor J R Firth.
Mitchell remained at SOAS until 1964 when he was appointed Professor of Contemporary English at the University of Leeds.
[1] Mitchell was also the author of Teach Yourself Colloquial Arabic subtitled "the living language of Egypt", first published in 1962.