Stokes was born in Plymouth, and educated at Blundell's School in Tiverton, Devon. In 1930 he commenced an engineering apprenticeship with Leyland Motors, which included further education at the Harris Institute of Technology in Preston. During the Second World War, Stokes served with the Royal Electrical and Mechanical Engineers, reaching the rank of lieutenant-colonel. In the early summer of 1939 he married Laura Elizabeth Courteney Lamb. Excepting the break for military service between 1939 and 1945, Stokes stayed with Leyland throughout his career, although he also served in the Territorial Army. In 1968 he was appointed chairman and managing director of British Leyland, a challenging role much in the public eye at the time.