 Blyth worked for Mobil Oil from 1963 to 1969, for General Foods from 1969 to 1971 and for Mars Foods from 1971 to 1974.Between 1974 and 1977, he was general manager of Lucas Batteries and between 1977 and 1981 general manager of Lucas Aerospace.He was also director of the Imperial Group from 1984 to 1986, managing director of Plessey Electronic Systems in 1985 and 1986, and managing director of the Plessey Company in 1986 and 1987.