Born in Edinburgh in 1906, John Innes Mackintosh Stewart was educated at Oriel College, Oxford, where he was presented with the Matthew Arnold Memorial Prize and named a Bishop Frazer's scholar. After graduation he went to Vienna to study Freudian psychoanalysis for a year.
His first book, an edition of Florio's translation of Montaigne, got him a lectureship at the University of Leeds. In later years he taught at the universities of Adelaide, Belfast and Oxford.
Under his pseudonym, Michael Innes, he wrote a highly successful series of mystery stories. His most famous character is John Appleby, who inspired a penchant for donnish detective fiction that lasts to this day. His other well-known character is Honeybath, the painter and rather reluctant detective, who first appeared in The Mysterious Commission, in 1975.
Stewart's last novel, Appleby and the Ospreys, appeared in 1986. He died aged eighty-eight.