Serial 5V:

Starring: Tom Baker (The Fourth Doctor)
, Matthew Waterhouse (Adric), Sarah Sutton (Nyssa), Janet Fielding (Tegan Jovanka), Peter Davison (The Fifth Doctor). 

When the Doctor and Adric go to Logopolis, planet of mat
hematicians, to fix the TARDIS's chameleon circuit, they instead fall into a trap of the Master's. The evil Time Lord seeks the secret behind Logopolis' replica of Earth's Pharos Project radio telescope but instead succeeds in unleashing a wave of entropy which threatens to consume the entire universe. The Doctor and the Master enter into an uneasy alliance and must rely on the help of only Adric, Nyssa, and an airline stewardess named Tegan Jovanka whose aunt was murdered by the Master. But then, in the moment of greatest crisis, the Master unveils his trump card, which may lead to either universal domination... or universal destruction.

Early in th
e development of Season Eighteen, when it had become clear that several of the year's stories being hampered by writing troubles, it was decided that script editor Christopher Bidmead would take the reins of the final serial. Bidmead and producer John Nathan-Turner already suspected that their star, Tom Baker, would be leaving Doctor Who at season's end -- a fact finally confirmed around September 1980 -- and were making plans for this eventuality. It was decided that the final two stories of the year, together with the first adventure of Season Nineteen, would form a trilogy. Logopolis, the middle installment -- featuring the Doctor's regeneration -- would be a tale of epic proportions, and Bidmead began presaging it in earlier serials, with the introduction of the concept of the Charged Vacuum Emboitment (CVE) in Full Circle. Executive producer Barry Letts handled some of the script editing chores on Logopolis, providing Bidmead with extensive notes on each episode.

Nathan-Turner and Bidmead were greatly concerned abou
t the effect that Baker's departure would have on Doctor Who's fan base. To help rectify the situation, they had already arranged for the return of arch-nemesis the Master in the season's penultimate story, The Keeper Of Traken. Further, they hoped to reintroduce an old companion in Logopolis who would accompany the Doctor for just three stories. However, both candidates -- Elisabeth Sladen (Sarah Jane Smith) and Louise Jameson (Leela) -- turned down the offer, with both feeling that regular work on Doctor Who was a part of their past. Consequently, the production team decided to devise a new companion, envisaged as a brash, smart but insecure air hostess. It was decided to make her Australian to try to break away from the standard companion mold. Nathan-Turner suggested her name be either Tegan or Jovanka; Bidmead misinterpreted this, and took her full name to be "Tegan Jovanka".

In September and Oct
ober, 109 actresses auditioned for the role of Tegan. Amongst the final group was young Australian actress Janet Fielding (the stage name of Janet Mahoney), whose work to date consisted mostly of fringe theatre and an episode of Hammer House Of Horror; she had been recommended to Nathan-Turner by a friend who cited her as the classic example of a "bossy Australian". When Nathan-Turner indicated his concern about both her age and her height, Fielding lied on both counts, claiming she was 20 years old (she was actually 23) and that Australian airlines had lower height standards. She would later fear that these deceptions would get her fired from the show, but this would not come to pass. Fielding won the role, and in early October was contracted for three stories. She was introduced to the press with a photocall on October 23rd.

At the same ti
me, Nathan-Turner was searching for a new Doctor to replace Baker. He was uncertain about what direction to take with the next incarnation, except that it had to be as different from Baker as possible. He approached well-known character actor Richard Griffiths, who was unavailable; Iain Cuthbertson (who had played Garron in The Ribos Operation two years earlier) also turned down the role. Finally, Nathan-Turner contacted Peter Davison, with whom he had worked on All Creatures Great And Small. Nathan-Turner felt that Davison's character on that show, Tristan Farnon, would be a good model for the new Doctor. Davison, however, was uncertain of playing another character similar to Tristan, was wary of becoming involved in such an institutionalised show as Doctor Who, and also believed that, at 29, he was too young to play the Doctor. He initially rejected Nathan-Turner's offer but later reversed his decision, as he could not now bear to see someone else win the role. News of the casting was leaked to the press on November 4th, and a press conference followed the next day.

The director
for Serial 5V was Peter Grimwade, who had earlier worked on Full Circle. Location filming around London was originally to run from December 16th to 18th. However, because of the need to remount the final studio day of The Keeper Of Traken on the 17th due to a labour dispute, an extra day was scheduled for the 19th, and later pushed back to the 22nd. Taping on this day occurred at the Barnet by-pass, where Nathan-Turner and Bidmead believed there existed one of the few remaining genuine police boxes (indeed, this had been one of Bidmead's early inspirations for Logopolis). However, it was discovered that this had recently been torn down due to vandalism; consequently, the old TARDIS exterior prop -- junked at the start of the season -- was brought back into use, doubling for the "real" police box.

Studio work then began with a two-day block
from Friday, January 8th, 1981, and continued with a three-day session beginning on Thursday the 22nd. The regeneration itself was recorded on January 9th, marking the official beginning of Davison's tenure on Doctor Who. On February 3rd, Nathan-Turner took the unusual step of composing two montages of clips from old episodes, based on suggestions from unofficial fan advisor Ian Levine. The first featured many past villains, including the skeletal Master (from The Deadly Assassin), a Dalek (Destiny Of The Daleks), the Captain (The Pirate Planet), the Cyberleader (Revenge Of The Cybermen), the Sontaran Stor (The Invasion Of Time), the Zygon Broton (Terror Of The Zygons), and the Black Guardian (The Armageddon Factor). The second featured all the Fourth Doctor's companions: Sarah Jane (Terror Of The Zygons), Harry Sullivan (The Sontaran Experiment), Brigadier Lethbridge-Stewart (Invasion Of The Dinosaurs), Leela (The Robots Of Death), K-9 (Mark I, to be precise; from The Armageddon Factor), the First Romana (The Stones Of Blood) and the Second Romana (Full Circle). In each case, the featured character is saying "Doctor".

Logopolis was actuall
y the end of several individuals' regular involvement with Doctor Who. Barry Letts' role as executive producer was by now seen as redundant, given that Nathan-Turner had gained considerable experience in the job over the course of the year; indeed, his involvement in Doctor Who had steadily lessened as Season Eighteen wore on. Although Letts would offer some further script commentary at the start of Season Nineteen, Logopolis was the final serial for which he received an on-screen credit.

Bidmead had also decided to leave the programme, belie
ving that he was not being suitably compensated for the amount of work his position demanded. He would, however, write two further Doctor Who stories (Castrovalva and Frontios) and novelise all three of his serials for Target Books. More recently, Bidmead has concentrated on writing articles about computer science for various magazines and journals. He was also one of the earliest Doctor Who professionals to have a visible presence in Who-related fora on the Internet.

Logopolis part
four aired on March 21st, bringing Season Eighteen and the record-setting Tom Baker era to its conclusion. Baker would experience a career lull directly after leaving Doctor Who, but eventually found himself once again in demand, on television, on stage and on the silver screen. He has appeared in such diverse product as Medics, The Hound Of The Baskervilles (for Barry Letts, playing Sherlock Holmes himself), the second series of BlackAdder, The Chronicles Of Narnia: The Silver Chair, American action-adventure drama Remington Steele, the feature film version of Dungeons & Dragons, and his own video autobiography, Doctor... Who On Earth Is Tom Baker. He has also done considerable voice work. Finally, Baker provided linking narration for the video release of the incomplete serial Shada, gave commentary on all his stories for the video Doctor Who: The Tom Baker Years and made an appearance in the thirtieth-anniversary charity special Dimensions In Time.