Donald Stevens was born in the East End of London, but grew up in Haywards Heath, the Sussex market town to which he was evacuated in 1939. In his early teenage years he became fascinated by aeroplanes and other machines, and on leaving school began training as a mechanical engineer. At 19, he joined the newly-formed design consultancy Norris Brothers Ltd as its first employee, and became a member of the design team for Donald Campbell's Bluebird hydroplane. Following National Service in the RAF, he became project co-ordinator for the design and construction of the 'Bluebird' car.