Gate (1980). Letts was not replaced, leaving Nathan-Turner as sole producer. Nathan-Turner cast Peter Davison as the Fifth Doctor for season 19, having previously worked with him on All Creatures Great and Small. Bidmead was briefly replaced with Antony Root, then more permanently with Eric Saward, who would work as script editor (and occasional writer) of the series from 1982 until 1986. After Nathan-Turner brought the Master back for three consecutive stories, The Keeper of Traken (1981), Logopolis (1981) and Castrovalva (1982, now played on a regular basis by Anthony Ainley), he believed that the show could benefit from the publicity inherent in bringing back popular characters and monsters from its past. Earthshock (1982) enjoyed considerable publicity from featuring the return of the Cybermen, after an absence of seven years. Season 20 then saw the return of Omega, the Mara, the Black and White Guardians (from the Key to Time season), and Brigadier Lethbridge-Stewart. The Daleks and Davros also returned in Resurrection of the Daleks (1984), but the re-use of classic villains often proved complex for script editor Eric Saward and the show's writers. Nathan-Turner, however, was largely focused on generating publicity for the series, something which he also achieved by the device of casting high profile, well-known actors (sometimes from the world of light entertainment) as guest stars. Nathan-Turner rarely used directors or writers who had worked for previous producers. The few exceptions were director Pennant Roberts (who directed Warriors of the Deep and Timelash), and the writers David Fisher (who wrote The Leisure Hive), Terrance Dicks (who wrote State of Decay and The Five Doctors), and Robert Holmes (who wrote The Caves of Androzani, The Two Doctors, The Mysterious Planet and the first episode of The Ultimate Foe). By coincidence, Nathan-Turner's tenure occurred during a period of large growth in the show's fan base in the United States, thanks to repeated showings there of the Tom Baker serials on affiliates of the American Public Broadcasting Service (PBS) network. Nathan-Turner became a familiar face among the many Doctor Who celebrities who made appearances during PBS fundraising drives, held to finance the purchase of more Doctor Who serials for screening in the United States. In addition to his work on the television series, for some years during the Eighties Nathan-Turner's interest in light entertainment led to him producing an annual Christmas Pantomime, at the Tunbridge Wells Theatre, starring the incumbent