Casting The serial introduces Janet Fielding in the role of Australian trainee
flight attendant Tegan Jovanka. Nathan-Turner conceived the role in collaboration with Bidmead, with the intention of introducing a younger female character who would display a superficial self-assurance masking inner vulnerability, without returning to the stereotype of screaming female companions of earlier serials. Brisbane-born Fielding had lost some of her native
Australian accent since emigrating to the UK in 1977, but revived her accent to audition successfully for the part. Nathan-Turner initially wished to reintroduce a former companion to provide continuity for viewers following Baker's regeneration, but created Tegan when
Elisabeth Sladen (
Sarah Jane Smith) and
Louise Jameson (
Leela) both declined to return for the duration of
season 19. Two cast members returned from the previous serial,
The Keeper of Traken: Sarah Sutton reprised her role as Nyssa, joining the TARDIS crew as a companion; and Anthony Ainley had his first full exposure in the role of the Master, a part he would continue to play for eight years. Outwardly, Ainley's beard and dark costume suggested close continuity with
Roger Delgado's portrayal in the early 1970s, but Ainley imbued his part with a greater focus on revenge and blackmail. The part of the mysterious Watcher was played by Adrian Gibbs; his part was left uncredited in order to foster a belief among fans that Peter Davison had played the role wrapped in white fabric. In fact, Davison's only appearance was during the final seconds of Part Four as the newly regenerated Doctor, for which he attracted a full actor's fee.
Filming , and a scale model was used instead. Drone shots of the telescope were included in the 2019 Blu-Ray DVD release For the outdoor scenes in Part One, in which Doctor materialises the TARDIS next to an actual
police box on Earth, the production team had initially planned to
film on location in a
layby on the
Barnet Bypass, in the outskirts of
North London. By the 1980s, police boxes had been obsolete for many years, but one of the last surviving boxes in Britain was still standing here, and it was intended to film the TARDIS prop standing next to the real police box. However, shortly before filming was due to take place, the production team discovered that the Barnet police box had been vandalised and subsequently demolished. Filming was re-located to a layby on the southbound side of the
A413 Amersham Road near
Denham, Buckinghamshire. An older TARDIS prop which had last been used in
season 17 was brought out of storage and assembled on location to stand in for the real police box. Today, the
M25 bridges the road where the scene was filmed. It had originally been intended to film the outdoor Pharos Project scenes in Part Four on location at the
Jodrell Bank Lovell Telescope in Cheshire, but this was precluded by budgetary constraints. Instead the exterior scenes were filmed at the BBC's receiving station in
Crowsley Park, and
miniature effect shots were created using a
scale model of a radio telescope. The scenes in the structure of the telescope were shot on
lighting gantry in the
Top of the Pops studio at
Television Centre, London. Incidental music in the serial was composed by
Paddy Kingsland, and includes
leitmotifs for Logopolis and the Watcher. In Part Four, an excerpt from
Symphony No. 8 by
Franz Schubert is heard playing on the technician's headphones in the Pharos Project control room.
Titles The closing titles sequence was recompiled with Tom Baker's face removed from the closing credits of Episode 4. The same opening and end title sequence and arrangement of the theme music was used for the following story,
Castrovalva, and next three seasons, but was altered to include Peter Davison's face. Episode 4 of this story was the last time, for the next 24 years, the lead character was listed in the credits as "Doctor Who" (thus making it the only time Peter Davison was credited as "Doctor Who"). Beginning with the next story,
Castrovalva, until the series's cancellation in 1989, the character was credited simply as "The Doctor". The
1996 television film did not have an on-screen credit for the
Eighth Doctor, but listed the
Seventh as the "Old Doctor". The
2005 relaunch returned the credit to "Doctor Who", and then again to "The Doctor" in "
The Christmas Invasion" (at the request of
David Tennant). Also, Episode 4 was the first to credit two actors as "Doctor Who" or "The Doctor" when a regeneration scene was involved. It also happened at the end of Episode 4 of
The Caves of Androzani (1984). In both instances, Peter Davison was billed second.
Outside references According to Christopher Bidmead, the Logopolitans employ a
hexadecimal, or base-16, numerical system, a real system commonly used in computer programming. When Adric and the Monitor read strings of numbers and letters, the letters are actually the numbers between 10 and 15, expressed as single digits. ==Broadcast and reception==