The Doctor tries to get Tegan home, but instead lands the TARDIS on a spaceship which is four days from Earth. He meets the frog-like Monarch from the ruined planet Urbanka, who explains that the ship carries three billion Urbankan refugees. But Monarch has visited the Earth four times in the past, and the vessel is also home to representatives of the ancient cultures of Australia, China, Greece and the Mayan Empire. However, as the time travellers explore, they soon realise that something about the humans is not right. And they grow suspicious that Monarch's benevolent facade masks sinister intentions.

The story originally intended to begin Peter Davison's tenure as the Fifth Doctor -- both in the studio and on screen -- was “Project Zeta-Sigma” by John Flanagan and Andrew McCulloch. By early 1981, however, it had become clear that Flanagan and McCulloch's ambitious scripts were not achievable on a Doctor Who budget. Former script editor Christopher H Bidmead agreed to develop Castrovalva in place of “Project Zeta-Sigma”, but it would not be ready in time for the start of Doctor Who's nineteenth recording block. Instead, producer John Nathan-Turner decided to bring forward Davison's sophomore adventure; this would also give the new star a chance to settle into the role of the Doctor before making the higher-stakes season premiere.

The serial in question was one of the first stories that Bidmead had set in motion for the Fifth Doctor, prior to his departure from Doctor Who. Terence Dudley had directed Meglos for the programme's eighteenth season, and while the production office agreed that his approach to making Doctor Who was not what they were looking for, it was suggested that Dudley should instead develop story ideas for the show. He initially proposed a murder-mystery set in the Twenties; this was not in line with Bidmead's science-oriented vision of Doctor Who, but it was later revived as Black Orchid. Instead, on August 29th, 1980, Dudley was commissioned to prepare a four-part outline envisaged as a satire on bureaucracy and megalomania. It came to be known as “Day Of Wrath” by the time full scripts were requested on December 23rd.

Four To Doomsday was one of the last serials to involve Barry Letts

Dudley wrote efficiently and so, when “Project Zeta-Sigma” was deemed unworkable, “Day Of Wrath” -- now retitled Four To Doomsday -- was available to replace it in the shooting schedule. Dudley's narrative was one of the last to see the involvement of executive producer Barry Letts, who was winding down his role on Doctor Who; however, he would not be credited for Four To Doomsday.

Meanwhile, work was ongoing to shape the Fifth Doctor. Davison was frustrated that he was given little indication of how to steer his portrayal, beyond drawing a marked contrast with Baker's incarnation. However, during Davison's December 3rd appearance on Pebble Mill At One -- a few weeks after it was announced that he would be Baker's successor -- a fan suggested that his Doctor should be “Tristan Farnon, with bravery and intellect”, referring to Davison's popular character on All Creatures Great And Small. Although Davison originally dismissed this notion, it stuck with him, and he eventually decided to use it as the basis for his performance after all. Davison was also determined to occasionally incorporate moments of whimsy, despite Nathan-Turner's insistence that jokiness in Doctor Who be minimised.

As with Season Eighteen, Nathan-Turner wanted the regular cast to wear distinctive costumes which would remain essentially the same from serial to serial. Not only would this save on wardrobe costs, but it was also seen as a way to increase Doctor Who's marketability. An early idea for the new Doctor would have seen him dressed in a morning suit with a collapsible topper. Subsequently, a polo outfit with jodhpurs was suggested. Davison liked the idea of a sports motif, but offered cricketing gear as an alternative, since this was a game that he played and enjoyed. Indeed, a photo of Davison in a charity cricket match had originally inspired Nathan-Turner to consider him for Doctor Who, and so the producer readily agreed.

The job of creating the Fifth Doctor's outfit then fell to Colin Lavers, who had been assigned as the costume designer for Four To Doomsday. One constraint imposed by Nathan-Turner was that the question-mark shirt collars, introduced during Tom Baker's final season, be retained. This was not to Davison's liking, because he felt that it made the Doctor's garments look contrived. Nathan-Turner also asked for something to adorn the Fifth Doctor's lapel, and decided -- out of the blue -- that a stick of celery would be appropriately quirky and unusual. Davison was baffled by this seemingly arbitrary decision, but the producer reassured him that an explanation would eventually appear on-screen.

Peter Davison lobbied to retain Nyssa, whom he felt best suited his Doctor

Another task confronting Nathan-Turner between seasons was to determine the future of the newly-expanded line-up of companions. The original plan had been for Adric and Tegan to accompany the Fifth Doctor. Nyssa was added to the TARDIS crew at a late date after Nathan-Turner grew fond of her portrayal in Johnny Byrne's scripts for The Keeper Of Traken. Around the start of March, Nathan-Turner decided to retain Nyssa throughout Season Nineteen; Davison had lobbied for the character, whom he felt best suited his vision of the Doctor. Adric, on the other hand, would be written out of Doctor Who before the end of the year, as it was generally agreed that the character had not worked out as originally envisaged.

By now, it was known that Season Nineteen would encompass only twenty-six episodes -- Doctor Who's standard length throughout the Seventies, but two episodes shorter than Season Eighteen. For Baker's final year, Nathan-Turner had lobbied for extra funds in order to do away with the six-part stories that he felt were no longer viable. Now, however, it was agreed that the budget for the additional episodes could be put towards A Girl's Best Friend, a fifty-minute pilot for a proposed spin-off series, K·9 And Company, to air around Christmas 1981.

These developments meant that the regular cast had to be issued revised contracts. Janet Fielding and Peter Davison were booked for all twenty-six episodes on February 18th and 20th, respectively. On the other hand, the 18th saw Sarah Sutton contracted for twenty-four episodes: Kinda, the story which would follow Four To Doomsday in the transmission order, had been conceived without Nyssa, and it could not plausibly be revised to include her except at the very beginning and end. Meanwhile, Matthew Waterhouse would appear in as few as twenty episodes; his contract was amended on February 25th.

For Season Nineteen, Nathan-Turner retained several design elements he had introduced the year before. These included Sid Sutton's title graphics, which were updated to replace Baker's face with Davison's. In addition, it was decided that Davison would be credited as “The Doctor” rather than “Doctor Who”, as had traditionally been the case. Sutton's costume was amended to include corduroy trousers, rather than the diaphanous skirt she had worn in Season Eighteen. Nathan-Turner preferred this image, and it would be more practical, especially during location filming. The change of attire would be explained in Castrovalva.

The director assigned to Four To Doomsday was John Black, who had previously handled The Keeper Of Traken. This would be his last Doctor Who serial, although he would also make A Girl's Best Friend. As Monarch, Black and Nathan-Turner cast Stratford Johns, who had been considered for the role of the Third Doctor in 1969. Johns was now eager to play characters who would offer a change from the popular police officer Charlie Barlow, whom he had played in Z Cars and various spin-offs. Nathan-Turner was now actively involved with the selection of guest performers, and was keen to attract as many big names to Doctor Who as possible to generate publicity.

On April 15th, a photocall was held to introduce Peter Davison in costume

Following a two-month break since the end of the eighteenth production block, work on Four To Doomsday began with a three-day studio session from April 13th to 15th at BBC Television Centre Studio 6 in White City, London. Waterhouse -- who had endured a difficult working relationship with Baker -- got off to a bad start with Davison as well, after he took it upon himself to point out mistakes he felt that his new colleague was making. The first day dealt with scenes in the control room of Monarch's spaceship and in the TARDIS, while work on the second day shifted to the Mobiliary and the surgery. The final day of the block centred on many of the scenes in the linkways, alongside those in the guest quarters and the library. A photocall was also held to introduce Davison in costume.

Cast and crew returned to TC6 for the second studio block, which ran from April 28th to 30th. At this point, Root was in the process of moving to another trainee appointment on Juliet Bravo, and was handing over to Doctor Who's new interim script editor, Eric Saward. Saward had written The Visitation, which would be the next serial into production. Taping began with the remaining linkways sequences -- including the Doctor's spacewalk -- along with modelwork. The opening shot of Monarch's spacecraft in flight was suggested by Nathan-Turner, who intended it as an homage to the start of the 1977 feature film Star Wars. The middle day was concerned with scenes in the recreational room and the flora room, leaving all of the material in the throne room for the final day of recording. By now, few were happy with Four To Doomsday: Davison was aggravated by plot holes, while Waterhouse felt that it emasculated Adric.

• Doctor Who Magazine #213, 8th June 1994, “Archive: Four To Doomsday” by Andrew Pixley, Marvel Comics UK Ltd.
• Doctor Who Magazine Special Edition #1, 2001, “Prince Charming” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #34, 2016, “Story 117: Four To Doomsday”, 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 #56, March 1995, “Production” edited by Anthony Brown, Cybermark Services.