The series was originally conceived as a vehicle for Dennis Waterman, after The Sweeney (1975) - in which Waterman co-starred - had finished the previous year. Initially, George Cole's character, Arthur Daley, was more of a secondary character, finding situations for Terry (Waterman) to get involved in each episode. But the great chemistry between the two characters quickly made itself apparent, and as a result Arthur was brought to the fore of storylines much more.