On Androzani Minor, the Doctor and Peri are mistaken for gunrunners and captured by General Chellak. Employed by Morgus, a powerful businessman, Chellak and his troops are trying to flush out the masked Sharaz Jek and his army of androids. At stake is a priceless supply of life-prolonging spectrox. Jek rescues the Doctor and Peri from execution, and they learn that he was betrayed by Morgus long ago, resulting in his disfigurement. But they also discover that they have contracted lethal spectrox toxaemia poisoning -- and it becomes clear that the Doctor will never find a cure in time to save both Peri and himself.

Upon reviewing a number of old Doctor Who serials shortly after joining the production office, script editor Eric Saward was particularly impressed with the work of one of his predecessors, Robert Holmes. In addition to serving as script editor, Holmes had contributed a number of Doctor Who scripts, latterly 1978's The Power Of Kroll. When the idea of a twentieth-anniversary special featuring every incarnation of the Doctor was mooted in 1982, Saward lobbied for Holmes to tackle the project. Producer John Nathan-Turner was reluctant, because he disliked working with writers who had preceded him on Doctor Who. He eventually demurred, but Holmes was uncomfortable using established characters, and his version of the special -- called “The Six Doctors” -- was ultimately abandoned, to be replaced by Terrance Dicks' The Five Doctors. Nonetheless, Saward remained eager to work with Holmes, and offered him carte blanche to provide a story for Doctor Who's twenty-first season. When Holmes and Saward met in the spring of 1983, the script editor had only one requirement: the adventure had to end with the regeneration of the Fifth Doctor.

Peter Davison had originally committed to three years as the Doctor, of which Season Twenty-One would be the last. Nathan-Turner had been optimistic that Davison would remain for at least a fourth season but, in March 1983, the actor had confirmed that he was not interested in extending his contract. Davison was now keen to try his hand at other types of roles, and had been disappointed with the quality of the scripts and production during Season Twenty. Around the same time, Davison's co-stars, Janet Fielding and Mark Strickson, informed Nathan-Turner that they would also be leaving Doctor Who in 1984.

Peter Davison was disappointed that he would not complete three full years as the Doctor

Nathan-Turner and Saward set about planning for all of these departures, as well as the introduction of a new companion, Peri Brown. Nathan-Turner decided to have the Doctor regenerate in the year's penultimate serial, which he felt would give viewers a chance to acclimate themselves to the Sixth Doctor before the long break between seasons. This decision disappointed Davison, who felt that he should have the opportunity to complete three full years as the Doctor. With the regeneration therefore set to occur in the sixth story of Season Twenty-One, it was agreed that the changeover of companions would happen in the two preceding serials, Resurrection Of The Daleks and Planet Of Fire.

When he was offered the chance to write the regeneration story, Holmes was enthused, since he knew that he would have even more freedom than usual in structuring his scripts. On May 6th, he was commissioned to write a storyline entitled “Chain Reaction”. At this point, the Doctor did not regenerate after succumbing to spectrox toxaemia, but simply because of exhaustion and the damage his body had sustained from Stotz and the other gunrunners. As was his wont, Holmes drew inspiration from a number of classic horror sources -- most notably the 1911 Gaston Leroux novel The Phantom Of The Opera, which had also inspired elements of Holmes' 1977 adventure The Talons Of Weng-Chiang.

By the time the scripts were requested on July 28th, the story's title had become The Caves Of Androzani. Nonetheless, the fan press reported that Holmes was writing a serial called “The Doctor's Wife”. This was how Nathan-Turner had listed the adventure on his planning board, in order to substantiate his long-held suspicion that somebody in the production office was leaking information about upcoming stories. The subterfuge would later inspire a genuine adventure for the Eleventh Doctor: 2011's The Doctor's Wife.

Saward made only a handful of changes to Holmes' scripts. At Davison's request, he concocted the explanation for the Fifth Doctor's decision to wear a celery stick on his lapel. The allergy to gases in the “Praxsis spectrum” made reference to the Praxis typewriter Saward used. More significantly, it was Saward who wrote the scene involving the Doctor's regeneration and the brief coda with the Sixth Doctor. Nathan-Turner wanted to repeat the success of the flashbacks which had accompanied the Fourth Doctor's regeneration in 1981's Logopolis, and so hallucinatory appearances by the Fifth Doctor's former companions were added to the script. At this stage, Nyssa was omitted because it was believed that theatrical commitments would prevent Sarah Sutton from appearing, while the Master was excluded due to concerns about Anthony Ainley's salary demands.

Graeme Harper was eager to invest The Caves Of Androzani with a realistic edge

The Caves Of Androzani would be directed by Graeme Harper, who had worked on Doctor Who for more than a decade, initially as an assistant floor manager and later as a production assistant. Although this would be his first directing credit on the show, Harper had previously handled a significant amount of 1981's troubled Warriors' Gate. Nathan-Turner agreed to hire Harper for The Caves Of Androzani after encountering him at a Christmas party in late 1982. Harper was eager to invest the serial with a realistic edge, which suggested the use of actual machine guns -- firing blanks -- rather than futuristic props.

Harper was ambitious in recruiting his cast for The Caves Of Androzani, and especially in his search for an actor with a distinctive voice to portray Sharaz Jek. Amongst others, Harper approached Tim Curry -- renowned for playing Transylvanian transvestite Dr Frank-N-Furter in the 1975 cult classic The Rocky Horror Picture Show -- and aspired to attract the interest of rock stars Mick Jagger and David Bowie. In the end, the part went to ballet dancer Christopher Gable, who had originally been considered for Salateen. Harper wanted to offer the role of Krelper to Michael Craze, who had played companion Ben Jackson in 1966 and 1967. However, Nathan-Turner had been unhappy with the results of a similar experiment in 1980, when original Doctor Who star Jacqueline Hill had played a new character in Meglos. He told Harper to hire someone else, and Roy Holder would ultimately portray Krelper.

Harper had hoped to take advantage of a lot of location filming for The Caves Of Androzani but, in the end, only three days -- from November 15th to 17th -- were available. These were for scenes on the surface of Androzani Minor, represented by the Masters Pit at Stokeford in Dorset. The area was popular for pheasant hunting, and so locals were paid to refrain from firing their guns for the duration of filming. Her lower legs bare to reflect the allegedly arid climate of Androzani Minor, Nicola Bryant developed mild frostbite on the first day at Stokeford.

Studio recording was then scheduled to begin with a two-day session on December 1st and 2nd. However, the BBC was once again hit by industrial action: a year earlier, a strike by the electricians' union had cost Doctor Who the final story of Season Twenty, and now the scenery shifters elected to walk off the job. While the dispute was settled in time to salvage the second studio block in mid-December, the two lost days would have to be made up. It was therefore decided that The Caves Of Androzani would take over the studio dates in early January 1984 originally intended for The Twin Dilemma, Colin Baker's debut adventure as the Sixth Doctor. Fortunately, Nathan-Turner was also able to arrange a new recording session for The Twin Dilemma, ensuring that Season Twenty-One would air in full. One concern about the revised dates for The Caves Of Androzani surrounded the availability of Maurice Roëves (Stotz), who lived in New York. It was feared that a new actor would have to be cast, with the location filming remounted, but the money was eventually secured to keep Roëves in the UK for the duration of the shoot.

Work at BBC Television Centre Studio 6 in White City, London finally got under way from December 15th to 17th. Scenes in the caverns and Morgus' office were scheduled for all three days, while the sets for Chellak's office, quarters and headquarters, as well as Jek's workshop, were in use on the first two days. Other recording during this block included material in the lift (on the initial day), the detention cell (on the middle day), and the control room of Stotz's ship (on the last day). Sharaz Jek's mask was painted in the manner of a Zulu warrior, based upon Harper's suggestion of using Masai face painting as a reference. The costume for the Magma Beast, constructed by the BBC Visual Effects Department, debuted on the 17th. Nathan-Turner was very disappointed by the finished product, although he had no choice but to allow taping to proceed. Much like the Myrka in Warriors Of The Deep at the start of the season, the Magma Beast costume was barely finished before it was needed in the studio. This left Colin Taylor, the performer inside the suit, very little time to become accustomed to it.

As the last day loomed, it became clear that Graeme Harper would be unable to complete all of the required material

After the holidays, cast and crew returned to TC6 for the rescheduled production block on January 11th and 12th. The first day dealt with scenes in the caves, the workshop and the armoury, plus Chellak's office and quarters. Harper had proved to be a meticulous director, often taping scenes shot by shot, and often with a handheld camera. The unfortunate consequence was that The Caves Of Androzani gradually fell badly behind schedule. As the last day of recording loomed, it became clear that Harper would be unable to complete all of the required material.

Working quickly, Holmes and Saward collaborated on ways to simplify the remaining sequences. The opening TARDIS scene was discarded, to be replaced with voiceovers dubbed over some location footage. As originally written, this would have depicted the Doctor studying the surface of Androzani Minor on the TARDIS scanner, and explaining that he wanted to collect sand in order to practise the art of glassblowing. Also dropped was a major action segment, in which the Doctor killed the Magma Beast by tricking it into falling over the edge of a chasm.

Even with these cuts and permission for a half-hour overrun, recording on January 12th still finished with only seconds to spare. The sets for the caves, the workshop and the armoury were again in use, as well as the TARDIS console room. Various effects shots were also completed, including the spectral appearances of the Fifth Doctor's previous companions. Because of the production's delay to January, Sutton was now available to appear as Nyssa, although she was suffering from chicken pox. Terms had also been agreed for Ainley to return as the Master, while Matthew Waterhouse signed a new agreement for his cameo as Adric. Fielding and Strickson were still under contract to play Tegan and Turlough, while Gerald Flood had already pre-recorded dialogue for the Kamelion android during the making of Planet Of Fire in October.

Also present on January 12th was Baker, recording his first moments as the Sixth Doctor. He had been formally contracted for this episode and The Twin Dilemma on September 30th. Baker was unable to fit into Davison's spare costume, and so he gave his performance with the trousers undone -- affording him the opportunity to moon Davison's wife, actress Sandra Dickinson.

The Fifth Doctor's era officially came to an end with the broadcast of The Caves Of Androzani in March. Once again, there were changes to the BBC's Friday schedule, with Episode Two preceding International Superstars on March 9th, before Davison's final appearance led into Match Of The Day Live on the 16th. Ironically, Davison was now regretting his decision to leave Doctor Who. He had been much happier with the scripts for Season Twenty-One -- and The Caves Of Androzani in particular -- and had become concerned about the lack of security which accompanied his departure from a regular job. However, these fears were quickly found to be unwarranted, as Davison would go on to develop one of the most respected and accomplished resumes in British television.

• Doctor Who Magazine #279, 30th June 1999, “Archive: The Caves Of Androzani” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #1, 2001, “Hide And Seek” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #39, 2018, “Story 135: The Caves Of Androzani”, edited by Mark Wright, Hachette Partworks Ltd.
• Doctor Who: The Eighties by David J Howe, Mark Stammers and Stephen James Walker (1996), Virgin Publishing.
• Doctor Who: The Handbook: The Fifth Doctor by David J Howe and Stephen James Walker (1995), Virgin Publishing.
• In·Vision #76, February 1998, “Production” edited by Anthony Brown, Cybermark Services.