The Doctor lands on Mars on November 21st, 2059. Bowie Base One, the first human colony on the Red Planet, has been established under the command of Captain Adelaide Brooke. However, the Doctor knows that it's destined to be destroyed in a nuclear explosion... today. Brooke is suspicious of the Doctor, but she needs his help when an intelligent contagion starts to possess her crew. The Doctor deduces that there is a connection with the glacier which provides the base's water. Yet he also knows that this event must happen: it is a pivotal moment in human history. Can he force himself to walk away without trying to save the day?

In mid-2006, it was decided that Doctor Who would be partly rested after its thirtieth season in 2008, with several specials filling the void until Season Thirty-One in 2010. However, it wasn't until April 2008 that the precise number and scheduling of these specials started to become clear. At that time, it was agreed that there would be four in total, which would air at Christmas 2008, Easter 2009, Christmas 2009, and at some point in 2010. It was now known that these specials would see David Tennant's exit from Doctor Who, alongside executive producers Russell T Davies and Julie Gardner. That year's Christmas special, The Next Doctor, was already in production, as the last entry in the Season Thirty recording calendar. It was written by Davies, who had also hoped to be solely responsible for scripting each of the three remaining adventures. But it was now clear that his commitments to the third season of the spin-off series Torchwood would preclude this. Reluctantly, he agreed to develop some of the specials in tandem with a co-author; Gardner insisted that Davies should retain a writing credit, in order to help attract the best possible guest cast.

As his collaborator on the 2009 Christmas special, Davies approached Phil Ford. Ford had already written for both Torchwood and Doctor Who's other spin-off series, The Sarah Jane Adventures, and had become a co-producer on the latter starting with its second season. Davies had wanted to bring Ford onto Doctor Who before the end of his tenure as its executive producer, and this was effectively his last opportunity to do so. Davies' inclination was to revive a storyline he had considered as a possibility for the 2008 Christmas special, in which the Doctor found himself in an eerie hotel while alien activity caused the Earth to be frozen in time. However, Davies was concerned about a key element of the narrative, which would have seen the Doctor exploring a deserted London. Fearful that the cost and logistics involved would be overwhelming, Davies began thinking about an adventure he dubbed “Christmas on Mars”. It was set in the middle of the twenty-first century, when humanity had established an outpost on the Red Planet.

On July 29th, Phil Ford submitted a storyline called “A Midwinter's Tale”

Davies presented the two story options to Ford on July 11th. The writer was eager to develop the hotel narrative, which was also Gardner's preference. Davies consented, and Ford submitted a storyline called “A Midwinter's Tale” on July 29th. Davies now discovered that the adventure had taken a turn firmly into sword-and-sorcery territory, emphasising the fantastical elements much more than he had envisaged. Ford's treatment also felt out of place as a Christmas special, appearing more suited to Hallowe'en. Davies decided to abandon “A Midwinter's Tale” and instead pursue “Christmas On Mars”.

Nonetheless, two key elements of “A Midwinter's Tale” would be retained. First, Davies intended “A Midwinter's Tale” to end with an Ood appearing before the Doctor, summoning him to the Ood-Sphere where the final adventure of his tenth incarnation would begin. This sequence would be retained as the capstone to “Christmas On Mars”. Second, Davies wanted the companion figure to be a strong, older woman. He hoped to end the Easter special with someone knocking on the TARDIS door, and the Doctor being flabbergasted to find Helen Mirren -- the star of programmes such as Prime Suspect and movies like The Queen -- standing on the other side. Another actress who fit the bill was Dame Judi Dench, a six-time Academy Award nominee who had won an Oscar for Shakespeare In Love; she was believed to be interested in a Doctor Who role. Whereas “A Midwinter's Tale” had paired the Doctor with a grandmother, “Christmas On Mars” would instead see him working alongside a mature woman who was the base's commander.

Davies and Ford met again on August 1st to discuss the replacement storyline. The day before, it was announced that NASA's Phoenix Mars Lander had discovered water on the Red Planet. This milestone inspired the aqueous nature of the entity which the Doctor would encounter, with Ford also drawing upon the animated water depicted in James Cameron's 1989 science-fiction film The Abyss. Furthermore, the scientific breakthrough helped convince Davies that he had made the right decision by dropping “A Midwinter's Tale” in favour of “Christmas On Mars”. He became enthusiastic about the idea that the narrative could be set within the lifetime of younger viewers, and so he was keen to take a realistic approach to the depiction of the human outpost. The writers also wanted the base personnel to be a distinctly multinational cohort, as in serials from the late Sixties such as The Moonbase and The Wheel In Space. In particular, it was suggested that the base commander might be Russian.

Phil Ford envisaged Mars as a terraformed world, where Camp Bowie had been established for decades

On August 7th, Ford delivered his new storyline under the title “Red Christmas” -- a play on the 1942 Irving Berlin tune White Christmas. Davies was unenthusiastic about this change, believing that it was redolent of low-grade horror fare. Most of the action was set at Camp Bowie, named after singer David Bowie, who released the hit song Life On Mars? in 1971. Ford envisaged Mars as a terraformed world, where Camp Bowie had been established for decades and its personnel flew great distances to various installations. Davies encouraged him to take a much more bare-bones approach, confining the action to Bowie Base: a rugged, isolated outpost on the untamed Martian frontier. Davies also had second thoughts about the base commander being Russian, which he feared was reminiscent of Mirren's turn as Tanya Kirbuk in the 1984 film 2010. Originally called Valentina Kerenski, her British incarnation was called Grace and then Adelaide, after Davies pointed out that Grace was the name of the Eighth Doctor's companion in Doctor Who (1996). The character's original Russian surname would ultimately be reassigned to Yuri.

At this point, Davies offered two significant additions to “Red Christmas”. The first was a service robot, which was inspired by the success of the 2008 animated film WALL-E. Davies' notion was that the robot would initially be clunky yet lovable, but might later go mad and become a threat to the Doctor; this notion ultimately went unused.

His other suggestion was the idea that the crew of Bowie Base was renowned throughout human history as Mars' lost pioneers -- a significant event which would be one of the “fixed points” in time mentioned in Season Thirty's The Fires Of Pompeii. Davies had promised Tennant that the specials would see his character taken in hitherto unexplored directions, and he now imagined the Doctor seizing upon his status as the last of the Time Lords to actually change a pivotal moment in history. Similarly, Davies had previously been opposed to the idea of the Doctor dealing with a problem by summoning the TARDIS via remote control. Now, he thought that such a solution would help establish the Doctor's emerging propensity to disregard the rules he used to follow. As such, a set piece would see the Doctor use the base's metal Christmas tree as a transmitter to contact his time machine; this would also address Gardner's concern that the storyline lacked festive elements.

By October, it had been decided that Tennant's final story, The End Of Time, would be split into two parts, once again throwing the broadcast plans for the latter specials into doubt. Davies felt that both installments of The End Of Time should be transmitted around Christmas 2009, and therefore “Red Christmas” might be brought forward to air around Hallowe'en after all. This would suit the story's spooky atmosphere, and would offer a better way to address the relative lack of yuletide touches. Later that month, an alternative plan had been decided: “Red Christmas” would air on Saturday, December 19th, with the two installments of The End Of Time following on Christmas Day and New Year's Day.

Russell T Davies decided to focus the script upon the Doctor's manipulation of history

Around mid-November, however, all of these plans were thrown into doubt as the production office found itself impacted by the financial crisis of 2008. It appeared that The End Of Time, which was intended to consist of two hour-long episodes, might instead have to be shortened to standard forty-five minute installments. The only alternative appeared to be the abandonment of “Red Christmas”, which was deemed the less essential of the remaining specials. Fortunately, by the end of the month, Gardner had managed to arrange the necessary funding to preserve the team's original plans. In the meantime, Davies had become determined to make “Red Christmas” a pivotal story. Consequently, he decided to focus the script upon the Doctor's manipulation of history, making this the transformative event which would lead into The End Of Time.

In mid-December, more money woes plagued “Red Christmas”. The 2009 Easter special, Planet Of The Dead, was supposed to mark Doctor Who's transition to High Definition recording. However, confusion within the BBC resulted in the abrupt loss of the funds which had been earmarked to facilitate the change of format. The only solution was to use some of the “Red Christmas” budget to make up the shortfall. As a result, Ford's vision of enormous, computer-generated water monsters attacking Bowie Base had to be abandoned. Instead, the Martian water would now carry an intelligence called the Flood. It would act like a contagion, infecting those with whom it came into contact, and mutating them into a monstrous form which could be realised using prosthetics.

The final major script issue that Davies had to confront involved the very last scene. As originally conceived, Adelaide survived the events of the story, rebuking the Doctor for his arrogance in breaking the Laws of Time and running off to rejoin her family. In mid-January 2009, however, both Davies and Gardner independently came to the conclusion that the story of the Doctor's hubris demanded that Adelaide had to die, taking her own life in order to preserve the course of history. Davies was aware that the suicide of a major character would be a controversial way to end a family programme, and so he was very careful to construct the revised scene in a manner which concentrated upon the Doctor's reaction, rather than the act of Adelaide's demise.

Cast as Adelaide Brooke was Lindsay Duncan, a Tony Award winner for the Broadway revival of Noel Coward's Private Lives. She would be working under director Graeme Harper, whose most recent Doctor Who assignment had been the Season Thirty finale, The Stolen Earth / Journey's End. “Red Christmas” would prove to be the final Doctor Who work of Harper's long and storied career, bringing an end to an association with the programme which stretched back to his days as a floor assistant in 1966. With regular Doctor Who producer Tracie Simpson busy overseeing the hectic post-production of Planet Of The Dead, Nikki Wilson filled in for “Red Christmas”. She was also the producer of The Sarah Jane Adventures, and had been the script editor of Season Thirty's The Sontaran Stratagem / The Poison Sky.

It was feared that the broadcast of a Doctor Who episode right before Christmas would be overlooked

Meanwhile, on February 6th, the BBC's schedulers informed the production team that the transmission plans for “Red Christmas” had changed again. It was now feared that the broadcast of a Doctor Who episode right before Christmas would be overlooked, especially given the massive publicity that The End Of Time was likely to generate. The Martian adventure would instead be brought forward to air sometime during the autumn. As a result, Davies had to remove most of the Christmas references from the script, and a new title was required. It was felt that the most likely airdate was now Saturday, November 21st, two days before Doctor Who's forty-sixth anniversary. The story's events were therefore set on November 21st, 2059 -- exactly fifty years into the future.

Production on the Autumn special began at Taff's Well Quarry in Taff's Well, which posed as the surface of Mars on February 23rd and 24th. The 25th and 26th were spent at the Great Glasshouse, part of the National Botanic Garden of Wales in Llanarthney; Davies had scripted the scenes in the Bio-Dome with this location in mind. One unexpected complication of recording in the Great Glasshouse was the loud and persistent birdsong, provoked by the bright lights set up by the crew. Davies duly amended the script to indicate that birds were housed in the Bio-Dome to control the insect population. After watching the rushes from Llanarthney, Davies became concerned that the appearance of the infected crewmembers was too scary for younger viewers. He found that the eerie contact lenses given to actors Chook Sibtain (Tarak) and Alan Ruscoe (Andy) were particularly dehumanising. It was agreed that Sharon Duncan-Brewster would not wear them when playing the infected Maggie Cain, given the character's considerable screen time, and appropriate changes were made to the dialogue. In some shots, the infected personnel would also now be filmed with their eyes closed.

February 27th took cast and crew to Victoria Place in Newport, for the final scene outside Adelaide's home. On the 28th, material in the control room of the Water Plant Dome was recorded in the Unisem Europe car park, on the Pen Y Fan Industrial Estate at Croespenmaen. Another car park -- this time on the premises of Next Generation Data in Newport -- offered a suitable space for Bowie Base's various connecting tunnels, corridors, airlocks and roof areas. Filming there took place from March 2nd to 4th, following a break on Sunday the 1st.

The rest of the shooting schedule was confined to Doctor Who's regular studio home in Upper Boat. The principal set was the Central Dome's Section A; it was erected in the space previously occupied by the Torchwood Hub, which had been destroyed in the opening episode of 2009's Children Of Earth. Harper started recording this material on March 5th and 6th, and then resumed after the weekend, from the 9th to the 12th. Part of the 9th was also spent taping the messages from home. In addition to the Central Dome, the set for the exit airlock was required on the 11th, because Davies had insisted that the Doctor's pivotal exchange via intercom with Adelaide should be performed in a single take. This was a departure from the normal practice, which would have involved filming Tennant's and Duncan's dialogue separately, and then editing the conversation together in post-production.

Work on March 13th began with the flashback to the young Adelaide's encounter with a Dalek. While an existing casing appeared in extreme close-ups, a computer-generated Dalek was primarily used. The rest of the day was spent on sequences in the Medical Dome, plus a pick-up shot of Roman. Harper filmed more action in the Medical Dome on March 14th, alongside material in the shuttle cockpit. After a day off on Sunday the 15th, he completed the Medical Dome scenes on the 16th, while also taping various inserts. The Section A set was redressed as Section F of the Central Dome for recording from March 17th to 20th. Footage in the TARDIS console room was also on Harper's itinerary for the 20th, alongside various effects shots.

Amongst the cuts to The Waters Of Mars were references to the waterborne intelligence as “the Flood”

The last filming for the Autumn special was a remount of the Doctor outside the TARDIS at the end of the story. It was recorded on May 15th at the Brandon Estate in Kennington, London during work on The End Of Time. By now, the adventure had received its final title: The Waters Of Mars. Some significant edits were required to bring the episode to a suitable length. Amongst the cuts were several sequences dealing with the romantic relationship between Yuri and Mia, as well as any references to the waterborne intelligence as “the Flood”. A portentous montage of clips reflecting upon the fate of the Time Lords was assembled for the Doctor's decision to change history; they came from Season Twenty-Eight's Rise Of The Cybermen and Doomsday, Season Twenty-Nine's Gridlock and Utopia, and Season Thirty's The Doctor's Daughter.

For a long time, The Waters Of Mars was indeed intended to air on November 21st, as the production team had anticipated. However, a late decision was made to bring the special forward to Sunday, November 15th and thereby avoid a collision with ITV's reality powerhouse The X Factor. Meanwhile, former Doctor Who producer, executive producer, director and writer Barry Letts passed away on October 9th. In recognition of Letts' enormous influence on Doctor Who, and on British television in general, The Waters Of Mars was dedicated to his memory.

• Doctor Who Magazine Special Edition #25, 8th July 2010, “The Waters Of Mars” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #61, 2016, “Story 201: The Waters Of Mars”, edited by John Ainsworth, Hachette Partworks Ltd.
• Doctor Who: The Writer's Tale -- The Final Chapter by Russell T Davies and Benjamin Cook (2010), BBC Books.