 Blyth was a director of Cadbury-Schweppes between 1986 and 1990, of British Aerospace between 1990 and 1994, and of NatWest between 1998 and 2000.In 1981, Blyth became head of defence sales for the Ministry of Defence, a post he held until 1985, when he was knighted.From 1987 to 1996, he was a chairman of the London Business School (LBS), and to 1998 director and chief executive of The Boots Company.