Mitchell-Innes, who was universally known as Mandy, played his one and only Test against South Africa in 1935, as an Oxford undergraduate.
He made his debut for Somerset while still a schoolboy at Sedburgh and was a prolific run gatherer for his university. Between 1934 and 1937 he scored a record 3319 runs at an average of 47.41 and it was during this run of remarkable form that he caught the eye of the England selectors.
Against the touring South Africans in 1935, he struck a brilliant 168 for his university in front of Plum Warner and was subsequently chosen for the Trent Bridge Test. He made only 5, but was retained for the second Test at Lord's. However a bout of hay fever forced him to withdraw. "I might be sneezing just as a catch came in the slips," he wrote to Warner. He joined up with the Oxford side at The Oval and scored another remarkable hundred against Surrey. He never got another chance to play for England.
In 1935-36 he toured Australia and New Zealand with the MCC, struggling with the bat, and the following summer he captained Oxford, enjoying the best of his four Varsity matches scoring 43 and 84 at the top of the order, although it was in a losing cause. He also captained the university golf team.
In 1936 he had a good summer with Somerset, but his career effectively ended when he joined the Sudan Political Service on leaving Oxford in 1937. He did play a few games when on annual leave, and when Somerset were desperate for players after the war he made another 24 appearances, captaining them four times. He failed, however, to show more than glimpses of his pre-war form.
In all, he played 132 first-class matches, scoring 6944 runs - with 13 centuries - at an average of 31.42. He also took 82 wickets at 34.79 apiece. A precocious talent, he once scored 302 not out in a house match for Sedburgh during a single afternoon, causing The Sedberghian to report: "Such cricketers rarely come this way."
He retired from the political service in 1954, returning to the north of England to become company secretary of a brewery.