A NASA probe discovers that the message “God save the Queen” was left on the surface of Mars more than a century ago. The Doctor, Bill and Nardole travel to the Red Planet in 1881 to investigate, and encounter a platoon of British soldiers. Colonel Godsacre explains that he found a crashed spaceship in the African veldt, aboard which was an Ice Warrior whom he's nicknamed “Friday”. Now the troops believe that they will be rewarded with riches excavated from beneath the Martian surface. But Friday's real goal is to free the Empress Iraxxa and her legions from stasis... while some of Godsacre's men have plans of their own.

Mark Gatiss' contribution to Doctor Who's thirty-fifth season, Sleep No More, had originally been envisaged as a two-part story which would reflect the way modern capitalism had upset the work-life balance. When it was decided that it would be reimagined as a standalone episode using a “found footage” format, Gatiss intended to revisit the more satirical elements in a follow-up adventure during Season Thirty-Six. He imagined the Doctor discovering that bankers in modern-day London had begun using sleep-abbreviating technology similar to the Morpheus Machines of Sleep No More, unleashing another wave of the monstrous Sandmen.

By early 2016, however, Gatiss had begun to ponder whether it was time for him to wind down his involvement with Doctor Who, given the forthcoming departure of his friend, Steven Moffat, as the show's executive producer. He still planned to write for Season Thirty-Six, but he was now mindful that it might potentially represent his final Doctor Who script. As such, while he and Moffat were working on the fourth and final season of Sherlock in March 2016, Gatiss asked if he could develop his dream adventure in lieu of the Sleep No More sequel. He had already reintroduced the Ice Warriors in Season Thirty-Three's Cold War, a claustrophobic story set aboard a Russian submarine. Now he wanted to pit the Ice Warriors against the Doctor on Mars itself. Although Doctor Who had visited the Red Planet on several occasions -- most recently, in 2009's The Waters Of Mars -- its most famous denizens had, to date, only appeared in other settings.

Consideration was given to having Winston Churchill unearthed during excavations on Mars

Moffat was not particularly enamoured of the Ice Warriors, but he reluctantly agreed on the condition that Gatiss develop the Martians in a novel manner. He was delighted with the writer's suggestion that a female Ice Warrior could be introduced for the first time, occupying a leadership position within Martian society. Gatiss' adventure was consequently scheduled as the tenth episode of Season Thirty-Six. Various additional ideas were considered over the weeks that followed. Actor Ian McNeice had indicated his interest in returning to the role of Winston Churchill, whom he had last played in 2011's The Wedding Of River Song, and consideration was given to having him be unearthed during excavations of the Martian surface.

Gatiss also contemplated revisiting the planet Peladon. Ice Warriors had appeared there as emissaries of the Galactic Federation in both 1972's The Curse Of Peladon and 1974's The Monster Of Peladon. Peladon's admission to the Federation in the earlier stories had drawn parallels with the United Kingdom's 1971 decision to join the European Economic Community. Given the June 23rd referendum on the country's membership in the European Union -- ultimately won by the “Brexit” movement which advocated for secession -- Gatiss thought that it would be timely to revisit that connection. This notion was abandoned due to Moffat's concern that Peladon's torch-lit stone passageways would be too similar to the tunnels and caverns of The Eaters Of Light, which Rona Munro was developing as Season Thirty-Six's ninth episode.

For a time, Gatiss intended that Grand Marshal Skaldak, the Ice Warrior who had appeared in Cold War, would return in the new story. However, he had also decided to draw upon the notion of Ice Warrior hives, which he had invented for dialogue in Season Thirty-Four's Robot Of Sherwood. Since this led to the inclusion of an extensive Martian burial chamber, Moffat was keen to avoid comparisons with the 1967 classic The Tomb Of The Cybermen. It was agreed that Gatiss' script would instead be set in the past, with the writer's favourite period -- the Victorian era -- quickly selected. Since Skaldak had been in suspended animation for centuries prior to the 1983 setting of Cold War, he would have to be omitted. Instead, the setting encouraged Gatiss to think in terms of period science-fiction stories such as Jules Verne's 1864 novel Voyage au centre de la Terre (that is, Journey To The Centre Of The Earth). The opening message on the Martian soil was inspired by a similar discovery on the lunar terrain in the 1964 film First Men In The Moon, an adaptation of HG Wells' 1901 novel.

Mark Gatiss hoped that his story could take place within a glass dome on the Martian surface

Gatiss hoped that his story could take place within a glass dome on the Martian surface, but the Doctor Who budget was unable to accommodate the concept. Amongst his supporting characters, Godsacre was given a surname that Gatiss had spotted in a Dorset cemetery. Vincey was so-called as an homage to characters in H Rider Haggard's seminal 1887 adventure novel She. Catchlove was inspired by Harry Flashman, a scoundrel created by Thomas Hughes for 1857's Tom Brown's School Days and later revived by George MacDonald Fraser for a series of novels which began with 1969's Flashman. Catchlove's name came from Stephanie Williams' 2011 book Running The Show.

Gatiss was writing his story by early August, and a first draft of the script was finished around mid-September. It was titled “The Empress Of Mars”, in reference to the various Barsoom novels by Edgar Rice Burroughs, such as 1917's A Princess Of Mars. At this stage, the British spaceship was a new vessel which was constructed after Godsacre discovered a psychic Gallifreyan book, hidden in a cave in South Africa. The Doctor later revealed that it was called Intergalactic Engineering For Dummies -- in reference to the series of instructional guides originally published by IDG Books, launched in 1991 with DOS For Dummies -- and that it was left in the cave after he misplaced it. The soldiers were assisted by a work gang made up of convicts from various parts of the British Empire; Jackdaw was amongst them. Friday had been found during the excavations on Mars, and the imprisoned Doctor later used the book to contact him telepathically -- addressing him by his real name, Vorka -- to ask for his help.

Both Nardole and Missy were later additions to the script, which had become Empress Of Mars by the start of December. It was also noted that the portrait of Queen Victoria seen in the officers' mess should resemble Pauline Collins' portrayal of the monarch in 2006's Tooth And Claw. Iraxxa's attitude towards humanity originally softened when Bill offered to take her place as Catchlove's hostage, rather than after Godsacre's surrender.

Having discovered that Vincey would be played by black actor Bayo Gbadamosi, Gatiss was initially concerned that his presence would appear anachronistic, given the Victorian timeframe. However, he subsequently learned about a Sudanese child named Mustapha who was adopted by soldiers of the Durham Light Infantry following the Battle of Ginnis on December 30th, 1885. Renamed James Durham, he subsequently enlisted as a soldier with the permission of Queen Victoria; Vincey was therefore given a similar backstory. At one stage, he was fatally stabbed by Catchlove after threatening to expose the other man's treachery, rather than being pushed into the path of an Ice Warrior weapon.

Missy's involvement suggested that The Eaters Of Light and Empress Of Mars should air in the opposite order

As episode ten, Empress Of Mars would immediately precede Season Thirty-Six's two-part finale, ultimately World Enough And Time / The Doctor Falls. However, a key story arc which had emerged for the latter part of the year was the potential redemption of Missy, the Doctor's Time Lord arch-enemy. In January 2017, Moffat realised that it was important for audiences to see this thread develop across several episodes, and he began to revise both The Eaters Of Light and Empress Of Mars accordingly. However, the nature of the opportunities for Missy's involvement in the two scripts suggested that they should air in the opposite order; hence Empress Of Mars would now be the season's ninth installment.

Gatiss' script joined episode eight, The Lie Of The Land, as part of Season Thirty-Six's sixth production block, under director Wayne Yip. On January 27th, the first scenes filmed for Empress Of Mars were those in NASA mission control -- actually the council chambers at Cardiff's County Hall. Material in the Martian tunnels was staged on January 31st and February 1st in the Redcliffe Caves, man-made excavations beneath the city of Bristol. The rest of the production was confined to Roath Lock Studios in Cardiff, starting with sequences at the base camp on February 2nd and 3rd; work on the latter day included some footage in Godsacre's tent and the brig.

Cast and crew had a day off on Saturday the 4th, while February 5th was devoted to location filming for The Lie Of The Land. Work on Empress Of Mars resumed on February 6th, the first of four consecutive days in the drilling area through to the 9th. Part of the latter day was also spent on further brig sequences, before production stood down on Friday the 10th and Saturday the 11th.

Yip's focus on February 12th and 13th was the set for the Ice Warrior hive. On the second day, he also taped more material in the drilling chamber and several inserts, while the Doctor and Bill leaving the message on the Martian surface was filmed on the Roath Lock car park with the aid of a green screen. The itinerary for February 14th included more recording in the brig and the drilling area, as well as additional pick-up shots. The hive set was then in use from the 15th to the 17th, while effects shots of Iraxxa emerging from the ground were also captured on the last day, prior to another break for the weekend.

On February 20th, Yip taped sequences in the TARDIS console room and the vault chamber at St Luke's University, plus an insert of the Doctor in the brig. Various pick-up and effects shots were then captured on the 22nd and 23rd; the first day also saw the recording of Bill's initial encounter with Catchlove in the tunnels.

On April 20th, Ysanne Churchman recorded Alpha Centauri's lines at the Audio Suite in Moseley, West Midlands. Now ninety-one years old, the actress had originated the character in The Curse Of Peladon and The Monster Of Peladon and, although she had largely retired from acting in 1993, she agreed to participate in Empress Of Mars. Unlike the character's previous appearances, when stuntman Stuart Fell had worn a costume to provide Alpha Centauri's physical form, the delegate was realised via computer animation on this occasion.

Empress Of Mars was scheduled for 7.15pm on June 10th, twenty minutes earlier than The Lie Of The Land the week before. The 1984 film Indiana Jones and The Temple Of Doom was its lead-in, while the quiz show Who Dares Wins returned to the slot after Doctor Who, following a week's hiatus.

• Doctor Who: The Complete History #88, 2019, “Story 273: Empress Of Mars”, edited by Mark Wright, Hachette Partworks Ltd.