An amnesiac Doctor is put on trial for his life by a Time Lord Inquisitor. The prosecutor, the sinister Valeyard, uses the Matrix to show the court the Doctor's recent adventure on the planet Ravolox. There, the robot Drathro rules an underground civilisation, but is now malfunctioning after centuries of operation. On the surface live the warlike Queen Katryca and her Tribe of the Free. They capture Peri and imprison her with Glitz and Dibber, two off-world conmen who have come to steal Drathro's secrets. Meanwhile, the Doctor discovers evidence of an impossible connection between Ravolox and Earth.

The first half of 1985 saw a succession of grim tidings confront Doctor Who producer John Nathan-Turner and script editor Eric Saward. First, the BBC decided to postpone production on Season Twenty-Three by a full year, from Spring 1985 to Spring 1986. This, in turn, would delay the start of transmission from January to September 1986. When Doctor Who returned, it would revert to its traditional twenty-five-minute format, as opposed to the forty-five-minute episodes which the production team had implemented for Season Twenty-Two. And, finally, Season Twenty-Three would consist of just fourteen episodes rather than the anticipated twenty-six, a change which was particularly demoralising for both cast and crew.

Under the circumstances, Nathan-Turner hoped that he might finally be assigned to a new programme after five years on Doctor Who, but Jonathan Powell, the BBC's Head of Series and Serials, asked him to remain for one more season. This would make Nathan-Turner the longest-serving producer in the programme's history. Saward had also contemplated his departure from Doctor Who, but his mould-breaking script for the Season Twenty-Two finale, Revelation Of The Daleks, encouraged him that he still had more invention to bring to the show. As such, Nathan-Turner and Saward began to plan for the future.

Michael Grade argued for the introduction of a new Doctor to revitalise Doctor Who in the eyes of the audience

The two men agreed that the shorter season necessitated a different approach, and Saward suggested that all fourteen episodes could be linked by an umbrella theme. They quickly settled on a scenario in which the Doctor was put on trial by the Time Lords -- effectively mirroring the series' real-life status. During a meeting with Nathan-Turner in late May, this notion gained the approval of Powell and the Controller of Programmes for BBC One, Michael Grade, although Grade argued for the introduction of a new Doctor to revitalise the programme in the eyes of the audience. Nathan-Turner successfully defended Colin Baker, suggesting that his lead actor just needed more time to win over the viewers. Grade directed the production team to cease the development of any scripts already under way for Season Twenty-Three, and start over again from scratch. He indicated that there should now be a greater emphasis on humour over violence, following repeated viewer complaints during Season Twenty-Two.

With Powell and Grade's assent, Nathan-Turner and Saward worked to establish the framework of the season-long story arc. The Doctor would be summoned for trial, with Time Lords from the future brought back to comprise the jury and administrators. The judge and the prosecutor had been selected anonymously by the vast Time Lord computer system known as the Matrix. However, as the season progressed, it would be revealed that this process had been corrupted -- raising suspicions as to the true motives of both characters. Eventually, the prosecutor would be unmasked as an evil future Doctor. The evidence in the trial would take the form of the Doctor's exploits; inspired by Charles Dickens' 1843 novel A Christmas Carol, there would be stories from the Doctor's past, present (his most recent adventure prior to the trial) and future.

Whereas Nathan-Turner had rejected Grade's advice to change his leading man, he felt that it was time to introduce a different companion. As such, Nicola Bryant's Peri would be killed off midway through the season, and the Doctor would be joined in the “future” segment by a new character named Melanie Bush. In the meantime, the relationship between the Doctor and Peri would be softened, as neither Baker nor Bryant had enjoyed the constant bickering which had defined their characters' rapport to date. An outline for Melanie was released on July 5th, indicating that she would be a computer programmer and fitness enthusiast from Pease Pottage, West Sussex. Also distributed that day were descriptions of the trial judge and prosecutor -- now known as the Inquisitor and the Valeyard, respectively.

The structure of Season Twenty-Three was of great concern to Nathan-Turner and Saward, since the limited number of episodes meant that there would be few opportunities to enjoy the “first night” boost of a new serial. After dismissing a format consisting of two four-part stories and a six-part finale, consideration was given to reserving one episode to set up the story arc and another to its resolution, bookending three four-part adventures. Soon, though, it was determined that there was no need to devote an entire episode to establishing the trial storyline. Instead, the year would begin with two four-part stories, before wrapping things up with three two-part narratives.

On July 9th, the first and fifth segments of the trial were assigned to Robert Holmes

This format was agreed upon in a meeting of the season's writing team on July 9th, where the first and fifth segments of the trial were assigned to Roberts Holmes. Holmes had last contributed 1985's The Two Doctors, although he had been working on “Yellow Fever And How To Cure It” for the original version of Season Twenty-Three. Saward valued Holmes' involvement; the two men enjoyed a good working relationship, with Saward regarding Holmes as a reliable veteran writer with a profound understanding of Doctor Who. Indeed, Holmes had played a key role in guiding the recruitment of the season's other writers: Philip Martin, David Halliwell and Jack Trevor Story. Holmes' scripts for the first four episodes of Season Twenty-Three were commissioned on September 2nd as “Wasteland”.

In the meantime, the saga of Doctor Who's long-term status continued to play out, both in the public eye and behind the scenes. The BBC's repeated disavowal of rumours about Season Twenty-Three's reduced episode count was undermined in July, when a fax which confirmed these details was accidentally sent to the Doctor Who Fan Club of America instead of Lionheart, the company which distributed the programme in the United States and Canada. Nonetheless, it took until December 18th before the BBC would publicly acknowledge the season's true length. On July 16th, former Doctor Who writer and director Terence Dudley -- who had most recently scripted 1983's The King's Demons -- wrote to Nathan-Turner, offering to replace him as producer if he wanted to move on. However, with the BBC unwilling to approve any of Nathan-Turner's other proposed projects, there was nowhere for him to move to.

On July 25th, Doctor Who returned to the airwaves -- albeit on radio -- with the debut of Slipback, a BBC Radio 4 production written by Saward and starring Baker and Bryant. Consisting of six ten-minute installments, broadcast two per week, Slipback was transmitted through August 8th as part of the Pirate Radio 4 programme. It was only the second original Doctor Who audio drama, following the Fourth Doctor story Doctor Who and The Pescatons, which had been released on LP by Argo Records in 1976. But while fans got to enjoy an extra adventure to help bridge the long wait until Season Twenty-Three, relations within the Doctor Who production office were beginning to fray. Amongst other grievances, Saward felt that Nathan-Turner was spending too much time wooing the programme's American fans, and was making poor choices in the actors and directors he brought onto Doctor Who. More and more, the script editor was working from home rather than in the production office.

Robert Holmes drew some elements of the narrative from his earlier Doctor Who work

As Holmes developed the trial's “past” segment, its title became “The Robots Of Ravolox” and then, by November, “The Mysterious Planet”. At one stage, Drathro was joined by another L3 robot called Jethro who had been severely damaged; however, this character was later replaced by Humker, Tandrell and the L1 service robot. Holmes drew some elements of the narrative from his earlier Doctor Who work: 1968's The Krotons had featured aliens who kept a more primitive civilisation cowed and who periodically claimed its two brightest youth, while humorous interplay between two conmen had been a hallmark of 1978's The Ribos Operation. Holmes delivered his scripts on January 15th, 1986, at which point he turned his attention to the season's concluding two-part story, “Time Inc”.

With the end of Doctor Who's year-long hiatus fast approaching, other pieces of the production puzzle were falling into place. Bryant was booked for her last eight episodes on November 28th. Meanwhile, Nathan-Turner had selected actress, singer and dancer Bonnie Langford to replace her. Given Langford's resemblance to Melanie's character outline, it may be that this had been the plan all along; she and Baker shared an agent, and the series star had recommended her to Nathan-Turner months earlier. Although Nathan-Turner was not confident of Langford's willingness to join the cast of Doctor Who, his offer came at a time when she was hoping that a dramatic role would help to expand her repertoire. In December, Langford signed a contract for the final six episodes of Season Twenty-Three, with options for two further years. This news was poorly received by Saward, who had already been unhappy with the development of Melanie as a character. He viewed Langford as another example of Nathan-Turner's penchant for burdening Doctor Who with inappropriate “light entertainment” performers.

On January 16th, Baker was contracted for Season Twenty-Three, with an option for fourteen more episodes to comprise Season Twenty-Four. He asked Nathan-Turner to consider overhauling the Doctor's garish costume for the new run, but the producer refused. Langford's casting was announced to the press on January 23rd. At the time, she was playing the title role in a stage production of Peter Pan, and she was joined by Baker for a photocall on its set. Like Saward, unofficial continuity adviser Ian Levine -- who had been instrumental in leading the public outcry against the postponement of Season Twenty-Three -- was appalled when he learned the identity of Baker's new co-star. Levine already felt that Nathan-Turner had been less than honest in their recent dealings, and the announcement of the new companion irrevocably shattered their relationship.

Jonathan Powell's scathing reaction to Robert Holmes' scripts was anything but routine

Meanwhile, Nicholas Mallett was assigned to direct “The Mysterious Planet”; it would be his first experience on Doctor Who. He began to prepare for filming while Holmes' scripts were sent for Powell's consideration, since he had now replaced Graeme MacDonald as the BBC's Head of Drama. Although this was a routine exercise, Powell's scathing reaction on February 24th was anything but. In an unusually detailed commentary, he took issue with several elements of “The Mysterious Planet”, objecting to the delay in establishing the trial scenario until Episode Two, the lack of clarity as to the nature of the crisis on Ravolox, and the extent of the Doctor's involvement in its resolution. Most frustratingly, Powell seemed to contradict Grade's edict that humour should feature more prominently in Season Twenty-Three, with some of his most stinging criticism reserved for the Doctor's taunting of the Valeyard and the comic banter between Glitz and Dibber. Powell argued that these elements undermined the high stakes of the Doctor's trial.

Holmes was deeply hurt by Powell's indictment of his scripts. To exacerbate the situation, the writer had been battling health problems for some time, and so it was an even greater concern that he would now have to suspend work on “Time Inc” in order to revisit “The Mysterious Planet”. Saward was livid, and felt that Powell had demonstrated a lack of respect for the veteran writer. Fortunately, Nathan-Turner and Mallett were able to convince Powell that only fairly minimal changes to Holmes' scripts were necessary. This included the deletion of an early scene depicting the Doctor and Peri in the TARDIS, which made way for the Doctor's earlier discovery of the nature of his trial, and the elimination of much of the invented slang from Glitz and Dibber's dialogue.

Nathan-Turner took the lead in casting several of the roles for “The Mysterious Planet”, given their importance beyond these four episodes. Both the Inquisitor and the Valeyard would be appearing throughout Season Twenty-Three, and Holmes was contemplating the return of Sabalom Glitz in “Time Inc”. For his part, Mallett suggested approaching the well-known comedy team of Dawn French and Jennifer Saunders to play Glitz and Dibber, only to learn that their schedules would not accommodate the planned recording dates. Instead, Nathan-Turner offered the role of Glitz to Tony Selby, and the Inquisitor to Lynda Bellingham; he had met both actors at a party held at the restaurant owned by Bellingham's husband. Bellingham was contracted for Season Twenty-Three on March 25th. Meanwhile, Michael Jayston agreed to play the Valeyard.

Virtually at the eleventh hour, Dominic Glynn was commissioned to create a new arrangement of the Doctor Who theme tune

When he became Doctor Who's producer in 1979, Nathan-Turner had decided to dispense with the practice of hiring freelance musicians to compose the score for each serial, and instead rely upon the services of the BBC Radiophonic Workshop. He was now rethinking this approach, and he decided to hire Dominic Glynn, a young freelance composer, for “The Mysterious Planet”. On March 27th -- virtually at the eleventh hour -- Nathan-Turner decided to commission Glynn to create a new arrangement of Ron Grainer's Doctor Who theme tune as well, replacing the Peter Howell version which had been introduced in 1980. The short notice meant that Glynn had to tackle the assignment before he had even finished setting up his home studio; he also had to deduce the melody by ear, since he had no time to acquire a copy of Grainer's sheet music.

To ensure that Doctor Who's return to the screen made a dazzling first impression, Nathan-Turner decided to spend lavishly on the opening footage of the TARDIS being drawn into the Time Lord space station. For the first time, a motion-controlled camera would be used for Doctor Who, trained upon an elaborate six-foot-wide model of the station. The forty-five-second shot, filmed at Peerless Studios in Elstree, Hertfordshire, took a week to complete and cost more than £8,000. This made it the most expensive sequence in Doctor Who to that point, although some of the cost would be defrayed by reusing parts of the footage for establishing shots throughout the season.

Meanwhile, although Saward had renewed his Doctor Who contract in March, he was now having second thoughts about continuing in his role as script editor. Indeed, Holmes had previously warned him that he had remained on the show for too long. Saward decided to take a leave of absence from the Doctor Who production office, which would give him some distance from Nathan-Turner and afford him the time to write the final episode of “Time Inc”, which Holmes was too ill to complete. Finally, on April 2nd, Saward resigned from Doctor Who. Powell denied Nathan-Turner's appeal for a replacement script editor, and instead encouraged him to try to repair his relationship with Saward. Otherwise, Nathan-Turner would have to act as both producer and script editor.

Recording for “The Mysterious Planet” began more than fourteen months after the end of production on Revelation Of The Daleks, when April 8th and 9th were spent in the Queen Elizabeth Country Park at Horndean, Hampshire for scenes in the wilds of Ravolox. Unusually, the same location had been used in Revelation Of The Daleks, albeit under wintry conditions which would help to disguise the duplication. Further differentiating the two serials was the decision that Doctor Who's location work would now be captured exclusively on Outside Broadcast (OB) videotape, which had only occasionally been employed in the past. The use of film, previously the default medium on location, would now be limited to model and effects shots; this would make editing easier, and ensure a better blend with studio footage, which was almost always recorded on video. On April 10th and 11th, the Tribe of the Free's camp was actually Butser Ancient Farm, a reconstruction of an Iron Age agricultural settlement in Chalton, Hampshire.

By now, Nathan-Turner had decided that the entirety of Season Twenty-Three would be treated as a single fourteen-episode story under the title The Trial Of A Time Lord. This was yet another decision with which Saward disagreed. Although he acknowledged the promotional possibilities inherent in making the longest Doctor Who adventure ever -- besting 1966's twelve-part The Daleks' Master Plan -- Saward feared that casual viewers would ultimately be dissuaded from watching the later installments.

Amidst all of the turmoil in the production office, studio rehearsals for The Trial Of A Time Lord's first segment conjured some drama of their own. Roger Brierley had been cast as Drathro, and it was intended that he would deliver his lines while inhabiting the robot costume constructed by the BBC Visual Effects Department. However, Brierley found the outfit claustrophobic and unwieldy, and he soon became adamant that his involvement be limited to providing Drathro's dialogue. Nathan-Turner initially believed that the role would have to be recast at short notice, but visual effects designer Mike Kelt had anticipated this development. Instead it was agreed that Kelt's assistant, Paul McGuinness, would operate Drathro, while Brierley read in his lines from off camera.

Work on The Trial Of A Time Lord resumed on April 24th and 25th at BBC Television Centre Studio 6 in White City, London. On both days, Mallett concentrated on scenes in the tunnels and subways; material in the hut where the Tribe kept their prisoners was also taped on the first day. Mallett subsequently alerted Nathan-Turner to his concern that Episodes Three and Four were badly underrunning. With Holmes too sick to contribute the necessary material, Nathan-Turner himself wrote two and a half minutes' worth of content, extending some of the courtroom material while adding an extra scene in which Broken Tooth and Balazar argued about the route to Drathro's “castle”.

When the cast and crew arrived in the studio on May 12th, the courtroom set was nowhere to be found

Recording for the first segment of The Trial Of A Time Lord was then intended to conclude with a three-day session in TC3 from May 10th to 12th. Work on the first two days involved the “castle” plus more action in the subways, notably the area around the doors to Drathro's lair. Sequences in the food production centre were also taped on the initial day of the block. The scenes in the courtroom were then scheduled for the last day, together with a remount of Drathro's final moments in the tunnels. Unfortunately, when the cast and crew arrived in TC3 on the morning of May 12th, the courtroom set was nowhere to be found. It transpired that it had been erected in the wrong studio and, when hurried attempts were made to assemble it in TC3, it was found to be too large and in need of modification. As a result of these delays, Mallett was unable to record the Doctor's arrival on the space station. Instead, this scene was remounted in TC6 on June 13th, during work on The Trial Of A Time Lord (Segment Two).

On August 19th, the BBC announced that Doctor Who had been renewed for a twenty-fourth season. The Trial Of A Time Lord Episode One then premiered on September 6th; the eighteen months which had elapsed since the concluding installment of Revelation Of The Daleks represented Doctor Who's longest absence from broadcast television to date. As with Season Twenty-Two, Doctor Who was scheduled for Saturday evenings, albeit at 5.45pm, twenty-five minutes later than in 1985. This timeslot had previously been occupied by the final season of The Dukes Of Hazzard. Doctor Who's new lead-in was the highly-touted variety show Roland Rat: The Series. Episode One was then followed by Telly Addicts, which was replaced by The Noel Edmonds Late Late Breakfast Show as of Episode Two.

By this time, Nathan-Turner had come to share Saward's fears that a fourteen-part story might struggle to maintain its viewership as the season progressed. As such, he began to write continuity announcements to recap events, and these began airing with Episode Three on September 20th. By that point, however, The Trial Of A Time Lord had already lost one-fifth of the 4.9 million viewers who had tuned in for the opening installment -- itself representing the smallest audience for a Doctor Who season premiere since The Smugglers in 1966. Although the diminished audiences could be attributed, at least in part, to the unexpectedly disastrous ratings which greeted Roland Rat: The Series, it nonetheless appeared that the court of public opinion had already delivered its verdict on Doctor Who...