Racing model developed from 18/80 Mark-II. Similar basic specification, but with dry-sump lubrication, twin-plug cylinder head, close ratio gearbox, cockpit-adjusted brakes and many other minor refinements. Four-seater open racing body. Only 5 built.

See magazine article:
The M.G. Mark III - Autocar May 16, 1930 (1.1-MB pdf)