The TARDIS lands on the frigid planet Svartos, where the Iceworld colony is ruled by the pitiless Kane. There, the Doctor and Melanie meet a time-displaced teenager from Earth called Ace, and are reunited with intergalactic rogue Sabalom Glitz. Glitz is searching for the treasure of the legendary Dragon which is supposed to dwell in the lower levels of Iceworld, unaware that he is doing so at Kane's behest. When Ace refuses Kane's offer to become one of his zombie-like mercenaries, she and Mel flee into the Iceworld tunnels, where Kane's millennia-old secrets wait to be discovered.

When he became Doctor Who's script editor in mid-January 1987, Andrew Cartmel contacted several up-and-coming writers he had met during his involvement with the BBC Script Unit. One was Ian Briggs, who had unsuccessfully pitched ideas for Doctor Who in the early Eighties. Briggs now developed “Clone The Drone” (or “Drone The Clone”), which Cartmel found cliched and derivative. He asked Briggs to try again, and indicated that he was looking for a fresh, innovative story which could be made entirely in the studio. It had now been decided that the final six episodes of Season Twenty-Four would consist of two three-part serials -- one made on location, the other in studio, and both by the same team. The year's location-based adventure would be Delta And The Bannermen, written by Briggs' Script Unit colleague Malcolm Kohll.

Briggs' next concept involved an intergalactic shopping centre. Its owner wanted to seize the TARDIS to take advantage of the real estate offered by its enormous interior dimensions, and the Doctor defeated him by resetting all of the store's prices to zero, collapsing the economy. Producer John Nathan-Turner was unhappy with the proposal, but Cartmel felt that it demonstrated the creativity he sought. He asked Briggs to refine his ideas, and the result was “Absolute Zero”. The intergalactic shopping centre had now become a trading colony on an ice planet, where a fourteen-year-old financial genius called Fatboy and his sidekick, Mr Spewey, sought a treasure hidden in its depths; the prize was ultimately revealed to be a living creature.

The narrative now took place on a frozen, pyramidal space station which was later revealed to be a massive warship

Cartmel was sufficiently happy with the Briggs' core ideas to commission a storyline on March 9th. However, he disliked its more farcical elements, especially since Delta And The Bannermen already had a distinctly comic bent. Consequently, Briggs developed the sinister Hess as the new villain of the piece. He also considered less melodramatic titles such as “Pyramid In Space” and “The Pyramid's Treasure”, reflecting the revised setting. The narrative now took place on a frozen, pyramidal space station which was later revealed to be a massive warship; the mysterious creature turned out to be an essential component missing from its power systems. The Doctor secretly allowed Hess to reactivate the vessel. Once it moved out of the shadow cast by the planet it orbited, the sun's rays caused Hess to melt.

Meanwhile, throughout the first half of 1987, there was doubt as to whether Bonnie Langford would continue to play Mel into Season Twenty-Five. To this end, on January 26th, an outline was issued for a potential companion called Alf. She was described as an independent-minded teenager, bored with her job as a supermarket cashier, who was whisked away from modern-day London by a time storm. Briggs was shown a copy of the outline, but he was asked not to use Alf in “The Pyramid's Treasure” due to the uncertainty regarding Langford's status.

Nonetheless, elements of Alf fed into Briggs' conception of one of his key supporting characters: Ace. At the time, he was tutoring drama at Questors Youth Theatre in Ealing, London, and the name came from the slang he heard his students using. In particular, three girls from Perivale named Anna-Marie, Joanne and Juno fuelled Ace, as did Judy Garland's performance as Dorothy Gale in the 1939 feature film The Wizard Of Oz. Indeed, Briggs' notes indicated that Ace's real name was, in fact, “Dorothy Gale”, although her surname was never stated on-screen. The production team took note of Ace as a possible replacement for Mel, along with the Welsh tomboy Ray whom Kohll had created for Delta And The Bannermen. Should Langford opt to leave Doctor Who at the end of Season Twenty-Four, either story could be positioned as the season finale, rewritten to have Ace or Ray join the Doctor.

On April 2nd, Briggs was asked to script the first episode of his adventure, now referred to as Dragonfire. The name change was necessitated by the decision to replace the orbiting Pyramid with the Iceworld complex situated on the planet Svartos (originally Tartros), which would be easier to realise. At this stage, Nathan-Turner suggested that the pirate character Razorback, also referred to as Swordfish, should be replaced by Sabalom Glitz, who had appeared the previous year in The Trial Of A Time Lord (Segment One) and The Trial Of A Time Lord (Segment Four). Nathan-Turner confirmed that actor Tony Selby would be available to reprise the role, for what would turn out to be the last time. Both Cartmel and Nathan-Turner were happy with Briggs' work on the opening installment, and so Episodes Two and Three were commissioned on April 13th. Some consideration had been given to making both Delta And The Bannermen and Dragonfire as Serial 7F but, by now, it had been decided that Briggs' story would be classified as Serial 7G.

Ian Briggs renamed his villain after the ruthless businessman Charles Foster Kane from the 1941 classic Citizen Kane

Ace's debt to The Wizard Of Oz was not the only element of Dragonfire steeped in cinematic history. When the news broke that Nazi war criminal Rudolph Hess was petitioning for release from prison, Briggs renamed his villain Kane, after the ruthless businessman and politician Charles Foster Kane from the 1941 Orson Welles classic Citizen Kane. Similarly, Hess' accomplice Krylla became Xana, from Charles Foster Kane's estate Xanadu. Briggs also made reference to Russian actor-director Vsevolod Pudovkin, Hungarian critic Béla Balázs, German critic Siegfried Kracauer, German-American critic Rudolph Arnheim, and French critic André Bazin. Bazin's partner was originally called Eisenstein after Russian director Sergei Eisenstein but, when it was noted that the plethora of foreign names might be construed as having racist overtones, he became McLuhan, for Canadian mass media theorist Herbert Marshall McLuhan.

Even more references were ultimately eliminated or went unacknowledged on-screen: another mercenary was named after American critic Andrew Sarris, Ace's boss was called Anderson for British director Lindsay Anderson, and a tannoy announcement referenced American critic Pauline Kael. Movies also gave rise to the Iceworld cafeteria, inspired by the Mos Eisley cantina in 1977's Star Wars, and the holographic messages from the dead, which mirrored Jor-El's message to his son in the 1978 version of Superman. The name of Glitz's spaceship and the manner of Kane's death both alluded to the pioneering 1922 horror film Nosferatu, Eine Symphonie Des Grauens (that is, Nosferatu, A Symphony Of Horror).

One substantial change made to Dragonfire involved Ace's relationship with Kane. Originally, she accepted his offer to become a mercenary, with the mark of his sovereign permanently imprinted on her palm. Ace rebelled only when ordered to kill Melanie. However, it was felt that these developments unnecessarily duplicated Belazs' backstory. Ace's stuffed dog companion, called Wayne, was also dropped. Briggs had maintained the Doctor's trait of mixing up proverbs, heard throughout the other stories of Season Twenty-Four, but Nathan-Turner and Cartmel had now decided to tone down some of the Seventh Doctor's more overtly comedic traits, and they were removed.

Like Delta And The Bannermen, Dragonfire would be directed by Chris Clough, who was responsible for casting the roles of Ace and Ray. The finalists for Ace were Sophie Aldred and Cassie Stuart; in fact, Aldred had originally put herself forward for Ray, since the part required the ability to ride a scooter, and she could drive a motorcycle. Both were invited for a second audition on May 26th, this time with Nathan-Turner in attendance. Stuart was the more experienced actress, having been in shows like Lovejoy and Blackadder, as well as films such as the 1984 Agatha Christie adaptation Ordeal By Innocence. But the job went to Aldred; it would be her first television work, although she would be seen as a presenter on the children's programme Corners before the broadcast of her Doctor Who debut.

Wanting a strong contrast with Mel, the production team concurred that Ace would accomplish this better than Ray

By June, there was still no firm word from Langford's agent as to whether his client would continue on Doctor Who. Nathan-Turner suggested that Melanie could be written out halfway through Season Twenty-Five, while the actress responded with an offer to appear in the first serial only. Finally, Nathan-Turner decided to write Mel out at the end of the current season. The production team now wanted the next companion to strike a strong contrast with Langford's character, and they concurred that Ace would accomplish this better than Ray. Nathan-Turner and Cartmel also felt that Dragonfire worked better as a season finale than the more lighthearted Delta And The Bannermen. On June 17th, Aldred was contracted for Dragonfire, with options for the entirety of Season Twenty-Five and eight episodes during Season Twenty-Six.

The first recording session for Dragonfire took place at BBC Television Centre Studio 1 in White City, London and spanned July 28th to 30th. On the first day, Nathan-Turner confirmed with Sylvester McCoy that his experiences with Aldred had been positive to date. The actress then accepted his offer to remain on Doctor Who for Season Twenty-Five. The set for the freezer centre was in use throughout the block, although the only work required there on the last day was a remount of footage involving Glitz, to address the fact that Selby's sideburns had been coloured too darkly. Other work on the first day included scenes in the cryogenics chamber, which was completed the following day. Taping then proceeded with sequences in the restricted zone, the flight cabin of the Nosferatu, Ace's quarters, and Kane's control room. More control room material was on the agenda for the last day of the session, as was action in the refreshment bar and the docking bays.

Given that Ace was largely adapted from Nathan-Turner and Cartmel's outline for Alf, Briggs agreed to relinquish any copyright claim on the character. He signed a legal document to this effect on August 3rd. The same day, he delivered revisions to the final scene of Dragonfire which reflected the changes in the TARDIS crew. Originally, Melanie pleaded with the Doctor to take Ace with them, but he seemed to ignore her. In fact, the Time Lord had already deduced that Glitz planned to invite Ace to journey with him aboard the Nosferatu II. McCoy now felt that the Doctor's farewell to Mel lacked impact, and he suggested making use of the audition piece which Cartmel had written for the role of the Seventh Doctor. This dialogue was strongly influenced by the non-linear perspective of chronology described by the super-powered Dr Manhattan in Alan Moore's 1986 comic book mini-series Watchmen, published by DC Comics.

Ineffective camera angles gave viewers the impression that the Doctor had spontaneously decided to dangle himself over a precipice

Work on both Dragonfire and Season Twenty-Four concluded on August 12th and 13th in TC3, during which Clough recorded all of the material in the caverns beneath Iceworld. Part of the first day was also spent on the final TARDIS sequence, while a photocall was held to announce Aldred as Doctor Who's latest companion. For Langford, on the other hand, this block would mark her departure from the programme. Amongst the last scenes to be recorded for Dragonfire was the -- quite literal -- cliffhanger to Episode One. As originally conceived, the Doctor was supposed to be following Glitz's map, only to find himself at the end of a passage; he then tried to scale the ice wall because he had nowhere else to go. Unfortunately, a combination of obscurity in the stage directions and ineffective camera angles would leave viewers with the impression that the Doctor had spontaneously decided to dangle himself over a precipice for no good reason!

Briggs' early drafts of Dragonfire had been very lengthy and, despite Cartmel's efforts to bring them down to size, all three installments still needed a number of cuts in post-production. One loss was a pair of scenes intended for Episode One, in which Glitz accidentally triggered a trap in the passages beneath Iceworld and was rescued by the Doctor in the nick of time. A cut from Episode Three included a reference to Iceworld customer Joanne Foxley, alluding to one of the girls who had helped inspire Ace. It would have come via the public address system; the announcer's voice was provided by Lynn Gardner, who had originally been cast as Ray in Delta And The Bannermen, until an injury forced her withdrawal. Clough cast her in Dragonfire by way of consolation.

Dragonfire Episode One was transmitted on November 23rd, Doctor Who's twenty-fourth anniversary, and led into the season finale of Brush Strokes. The serial's last two installments were instead followed by The Kenny Everett Television Show. Doctor Who then ended its own run on December 7th, wrapping up a year of turbulent reinvention. The next regular occupant of its timeslot would be the consumer affairs show Watchdog.

Meanwhile, in late August, Nathan-Turner had been informed by the BBC that Doctor Who was being renewed for its twenty-fifth season. Although the producer had been keen to move on to new projects, he was excited by the prospect of the show's silver anniversary, and so he agreed to remain on Doctor Who for an eighth season. However, as Season Twenty-Four unfolded on television screens, the weak ratings which Doctor Who had suffered during 1986 continued to plague the programme, exacerbated by bruising competition from Coronation Street. Having courted the programme's fans ever since he became producer, Nathan-Turner now found more and more of them demanding his removal. It was hard to quell the feeling that Doctor Who would be reaching the quarter-century mark under a dark cloud...

• Doctor Who Magazine #255, 27th August 1997, “Archive: Dragonfire” by Andrew Pixley, Marvel Comics UK Ltd.
• Doctor Who Magazine Special Edition #10, 13th April 2005, “Crazy Crazy Nights” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #44, 2017, “Story 147: Dragonfire”, 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 Seventh Doctor by David J Howe and Stephen James Walker (1998), Virgin Publishing.
• In·Vision #94, January 2001, “Production” edited by Anthony Brown, Cybermark Services.