The year is 1983, in the midst of the Cold War between the United States and the Soviet Union. The TARDIS materialises aboard a Russian submarine which is transporting Professor Grisenko to Moscow. He is escorting a block of ice, discovered during drilling operations, in which something is entombed. Against Grisenko's wishes, the creature is freed... and turns out to be Grand Marshal Skaldak, an Ice Warrior who has lain frozen for five thousand years. When the Soviets react with fear and hostility, Skaldak declares war on the human race -- and the Doctor must stop him from taking control of the submarine's nuclear arsenal.

During the six seasons which had followed Doctor Who's return to television in 2005, most of the classic monsters introduced during its twentieth-century iteration had been resurrected. A notable exception was the Ice Warriors, the militant Martians introduced by Brian Hayles in 1967's The Ice Warriors. The race had last appeared in 1974's The Monster Of Peladon, although there had been plans to pit them against the Sixth Doctor in “Mission To Magnus”, a script by Philip Martin which was scuppered when the 1986 season was retooled to consist solely of The Trial Of A Time Lord. Mark Gatiss, who had written several scripts for Doctor Who since 2005 -- most recently Season Thirty-Two's Night Terrors -- was eager to try his hand at an Ice Warrior story. However, he met resistance from Doctor Who executive producer Steven Moffat, who feared that the Martians were precisely the kind of slow-moving, incomprehensible monster that invited ridicule.

To overcome Moffat's reticence, Gatiss suggested surprising audiences by unveiling the previously-unseen creature which inhabited the Ice Warrior armour. It could then be far more nimble and dynamic than the Martians which had previously been depicted in Doctor Who. Moffat was intrigued by this concept, and it was decided that Gatiss would develop it for Season Thirty-Three. Separately, Gatiss had also pitched the idea of an adventure which took place aboard a nuclear submarine. The writer was fond of this environment, and especially films like Das Boot (1981), which was set aboard a German U-boat during the Second World War. He and Moffat quickly agreed that such a setting could be paired with the reimagined Ice Warrior concept. Gatiss positioned the events of his narrative in the early Eighties: the height of the Cold War between the United States and the Soviet Union, which was amplified by the two nations' burgeoning nuclear arsenals.

Skaldak was originally a time traveller from the 31st century who planned to provoke a nuclear war

The first draft, appropriately entitled Cold War, was completed in mid-October 2011. At this point, the Ice Warrior Skaldak was a more complex creation: he was a time traveller from the thirty-first century who planned to provoke a nuclear war which would wipe out humanity, thereby preventing mankind from dominating Mars in his era. After mind-controlling the Doctor's new companion -- at this point, a Victorian-era governess named Beryl -- to further his scheme, Skaldak was ultimately killed by one of the Russians. The surviving crew escaped to a British sub, the HMS Redoubt, while the sinking Soviet vessel -- not yet called the Firebird -- was destroyed by the water pressure.

Gatiss continued to work on Cold War throughout the early months of 2012. In late January, the Doctor Who production team decided that the new companion should hail from the twenty-first century rather than the nineteenth, and so Gatiss duly replaced Beryl with Clara. Skaldak's future origins and the Redoubt were dropped, while a second Soviet submarine was briefly introduced, which would rescue Captain Zhukov and his lieutenant. Until a late stage, Grisenko was to play a villainous role, striving to preserve the Ice Warrior as a weapon for the Kremlin. For a time, Skaldak sacrificed himself to destroy the submarine and its nuclear payload.

Several of the character names were devised in reference to Russian history and culture. Lieutenant Stepashin nodded to Sergei Stepashin, who was Prime Minister of Russia in 1999 under President Boris Yeltsin. Early drafts instead applied the surname to the political officer, who eventually became Belevich; at this point, the lieutenant was called Tsarsko. The navigator was originally Serovian before becoming Onegin, an allusion to Alexander Pushkin's verse novel Eugene Onegin, which was serialised from 1825. The captain took his last name from General Georgy Zhukov of the Red Army, who had been instrumental in the liberation of Eastern Europe from the Axis powers during the Second World War.

Around May, problems with the script for the 2012 Christmas special, The Snowmen, prompted the decision to put Cold War into production earlier than anticipated. As a result, Gatiss hastily completed his revisions ahead of a mid-June start to the filming. Cold War would now be the only story made as part of Season Thirty-Three's fifth recording block under director Douglas Mackinnon, who had just completed The Power Of Three. The services of not one but two erstwhile Doctors were secured for the episode: David Warner (Grisenko) had played an alternative Third Doctor in Big Finish Productions' Doctor Who Unbound releases Sympathy For The Devil (2003) and Masters Of War (2008), while Liam Cunningham (Zhukov) was once a favourite to win the role of the Eighth Doctor in what became the Doctor Who (1996) telefilm.

To accommodate the Ice Warrior costume, the submarine was largely realised in the studio

The new Ice Warrior costume was constructed by Neill Gorton and his team at Millennium FX. While respecting Gatiss' desire that it should hew as closely as possible to the original Ice Warrior design, Gorton effected some changes to make the armour more credible: the hands had digits rather than clamps, the proportions were better balanced, and the tufts of fur were removed. Indeed, in some ways, the overall conception of the new Ice Warrior better adhered to Hayles' original vision of the Martians as partly cybernetic creatures. To accommodate such a massive costume -- as well as to provide more space for the cast and crew -- scenes aboard the Firebird would largely have to be realised in the studio, since a real submarine would be far too cramped.

Work on Cold War therefore began with two weeks at Roath Lock Studios, Doctor Who's regular facilities in Cardiff. Corridor scenes were the focus on June 13th and 14th, before Mackinnon moved to the laboratory set on the 15th. After the weekend, June 18th concentrated on material in the torpedo chamber, alongside further laboratory and corridor shots. To the greatest extent possible, the team was determined to realise Cold War using practical effects; consequently, many of the sequences involving the unarmoured Skaldak were achieved using a puppet. June 19th saw various scenes taped in the torpedo chamber, the missile silo, the corridor and the laboratory. Cameras were rolling on the submarine's bridge from the 20th -- when Mackinnon also recorded additional laboratory footage -- to the 22nd. Part of the latter day was spent on more action in the corridors, while the material on the conning tower was shot against a green screen erected just outside the studio.

The cast and crew enjoyed another weekend off before venturing to the sole location for Cold War on June 25th. This was the premises of Newport Galvanizers, at the Llanwern steelworks in Newport, which offered a space suitable for the engine room. Then it was back to Roath Lock on the 26th, for additional recording on the lab set and the adjacent corridor. More bridge and corridor scenes were on Mackinnon's itinerary for June 27th and 28th; he also captured inserts of the bridge instruments on the 29th. The last stage of production for the episode involved the underwater shots of the Firebird exterior. It had been decided that the submarine would be realised as a model, rather than via computer animation, in order to provide a better sense of weight and presence. Mike Tucker and his company, the Model Unit, filmed these sequences at Halliford Film Studios in Shepperton, Surrey from September 4th to 6th.

Cold War was broadcast on April 13th, 2013. On this occasion, Doctor Who's lead-in was a repeat of Wallace And Gromit: A Matter Of Loaf And Death, as well as a news update. Since the stop-motion comedy was shorter than the installments of Pointless Celebrities which had preceded the first two 2013 episodes of Doctor Who, Cold War aired fifteen minutes earlier, at 6.00pm.

• Doctor Who Magazine Special Edition #37, Autumn 2014, “Cold War” by Andrew Pixley, Panini UK Ltd.
• Doctor Who: The Complete History #73, 2016, “Story 234: Cold War”, edited by John Ainsworth, Hachette Partworks Ltd.