The production team were sufficiently impressed that they kept him in mind and cast him in a supporting role in the 1973 story Carnival of Monsters,[7] broadcast as part of the tenth season of the programme.

The following year, Marter was cast in the role of Harry Sullivan, a character developed by the production team on the basis that the incoming Fourth Doctor could be portrayed by an older actor who would not be able to handle the more physical action scenes.

Books Marter's acting career beyond Doctor Who comprised mainly roles in episodes of series such as the BBC's The Brothers (1972), Crown Court, Bergerac (1981) and Granada Television's The Return of Sherlock Holmes (1986).

[5] He also had minor roles in several films, such as Doctor Faustus (1967), The Abominable Dr. Phibes (1971), North and South, The Medusa Touch (1978), and the comedy short The Waterloo Bridge Handicap (1978).

[14] In addition to his Doctor Who novelisations, Marter wrote adaptations of several 1980s American films such as Splash and Down and Out in Beverly Hills for Target and its imprint, Star Books.