Joseph returned to Birmingham to pursue a career in the engineering sector. On 17 November 1925 the partnership between Joseph and two others in the
Tyseley Munitions Works, operating as breakers down of service ammunition and fuses, was dissolved. In early 1939 Simpson bought the assets of the bankrupt
New Imperial Motors motorcycle company, which become part of his Clifford Aero & Auto Ltd. group, and produced components for
Lancaster and
Spitfire aircraft during the war. Post war, under the name of Clifford Cultivators Ltd., he produced
rotary cultivators from 1946 to 1959, as well as hand and power pumps, electric washing machines, and fork lift trucks, while his company Clifford Covering Ltd. manufactured
steering wheels. Clifford Aero & Auto was wound up in 1976. ==Honours and awards==