The Doctor, Amy and Rory find themselves in what appears to be an Eighties-era hotel on Earth. But they quickly discover that the outer doors and windows open onto walls, while the rooms and corridors move about, separating them from the TARDIS. Soon they encounter a small band of humans and aliens, and learn that there is a room for each of them, somewhere in the hotel, containing their deepest fear. Once they find it, they will inevitably begin to worship a mysterious entity which stalks the hotel, killing those who praise it. One by one, the hotel claims its victims... and even Amy cannot resist its lure.

In 2009, Toby Whithouse was commissioned to write a script for Doctor Who's thirty-first season. As a starting point, executive producer Steven Moffat proposed a story in which the Doctor became trapped in a maze-like hotel, where the geography was constantly shifting. In the past, Moffat had often found himself disconcerted by the experience of staying in a hotel, which suggested that such an environment could be effective in Doctor Who. He was eager to avoid the cliche of an eerie old Victorian establishment, and so Whithouse drew upon dreadful family vacations of his youth and instead opted for a tacky Eighties hotel. He saw the adventure as being tonally similar to Sapphire & Steel, the surreal science-fantasy programme created by Peter J Hammond in 1979.

The maze element inspired Whithouse to include a Creature akin to the Minotaur of Greek mythology, a half-man half-bull abomination who was confined to a labyrinth by King Minos of Crete. Doctor Who had featured similar monsters in the past -- in 1968's The Mind Robber, 1972's The Time Monster and 1979's The Horns Of Nimon -- but Whithouse was keen to put his own spin on the concept. The legendary Minotaur devoured youths who were sent from Athens to Crete as tribute; in Whithouse's narrative, they became the hotel's captives, who would ultimately be compelled to worship and feed the Creature.

The God Complex was planned to be the sixth episode of Season 31

Whithouse's adventure, entitled The God Complex, was planned to be the sixth episode of Season Thirty-One. However, during the writing process, it was decided that the labyrinth at the heart of the narrative was too much like the Maze of the Dead in the preceding story, The Time Of Angels / Flesh And Stone. Moffat asked Whithouse to instead develop a replacement script; this would become The Vampires Of Venice. The intention was to resurrect The God Complex the following year, and Whithouse duly resumed working on it in late 2010. It was now positioned as the tenth episode of Season Thirty-Two, although the addition of The Girl Who Waited to the schedule ultimately pushed it to the eleventh spot.

Throughout The God Complex, Whithouse wanted to illustrate examples of faith beyond the purely religious; hence Joe was associated with luck, and Howie with conspiracy theories. Nonetheless, the writer also intended to include a prominent and sympathetic character who would exhibit a more traditional faith in God. Although Whithouse was not particularly religious himself, he hoped to buck the often cynical trend in modern fiction of portraying devout individuals in a strictly negative light. He considered having this character be a Christian, but he eventually decided that it would be more interesting to portray a different religion, and opted to make Rita a Muslim.

Early drafts of The God Complex included an additional human character called Edward, a conservative blowhard who placed his faith in authority. To provide more variety, Edward evolved into the alien Gibbis, who exhibited more extreme and comical versions of the same traits. Gibbis was conceived as a largely unpleasant figure, but this element was gradually toned down. The policewoman in the pre-credits teaser was initially called Lucy Miller. Her surname was changed to Hayward to distinguish her from Lucie Miller, the companion portrayed by Sheridan Smith in Eighth Doctor audio plays from Big Finish Productions.

A late change to The God Complex came in January 2011, when executive producer Beth Willis voiced her concern that the story relied too heavily on abstract concepts and would be visually repetitive. To take better advantage of the hotel setting, Whithouse and Moffat developed the idea that there would be a room in the hotel for each of the trapped individuals, containing their specific worst nightmares. The notion of every person having their own version of Hell was partly inspired by Whithouse's work on his show Being Human, in which the third-season premiere had depicted characters consigned to Purgatory. Amy's room was specified as Number 7, reflecting her age when she first met the Doctor at the start of The Eleventh Hour.

David Walliams had collaborated with Mark Gatiss on comedy sketches for a BBC Two Doctor Who night in 1999

Nick Hurran was assigned to direct both The God Complex and The Girl Who Waited as Block Five (although it was actually the sixth production block of the overall recording schedule). Together, these two stories would usher in the next stage of the Doctor's relationship with Amy and Rory, culminating in their departure from the TARDIS after the Doctor concluded that he could no longer place them in regular danger. Amongst the cast was David Walliams, playing Gibbis. A longtime Doctor Who fan dating back to the mid-Seventies, when Tom Baker played the Fourth Doctor, Walliams was now well-known as one half of the comedy team behind Little Britain. He was also a good friend of regular Doctor Who scriptwriter Mark Gatiss, with whom he had collaborated on several comedy sketches for a BBC Two Doctor Who night in 1999. The same year, Walliams had appeared in Gatiss' Phantasmagoria, a Fifth Doctor audio play from Big Finish Productions.

One of the first tasks which fell to Hurran's team was to collect the portraits which would appear on the walls of the hotel. They would consist of a mix of doctored publicity photos -- for monsters such as a Sontaran, a Judoon and a Catkind -- and new pictures taken of BBC Wales staffmembers. The latter included Willis, producer Marcus Wilson (“Royston Luke Gold”) and petty cash buyer Kate Wilson (“Lady Silver-Tear”). Meanwhile, the Minotaur costume was constructed by Millennium FX on a body cast of actor and former kickboxing champion Spencer Wilding. Although Wilding stood two metres tall, the Minotaur was given additional height by building up the hoof-like feet. The complex headpiece featured twelve points of movement, requiring two operators to control. Some aspects of Whithouse's description were omitted from the final design, such as an armoured breastplate and a helmet which the Minotaur was to remove as he lay dying.

Recording for The God Complex began with two days of corridor scenes, taped at Doctor Who's usual studio facilities in Upper Boat on February 16th and 17th. The 18th was spent at the Seabank Hotel in Porthcawl for material in the reception area. After the weekend, sequences in the dining room and the kitchen were filmed at the Manor Parc Hotel in Cardiff on February 21st and 22nd. Cast and crew returned to Upper Boat on the 23rd and 24th. More corridor sequences were on the agenda for the first day, alongside those in Room 7, for which Caitlin Blackwood made her third appearance as the young Amelia. On the second day, the bedroom set was redressed as Room 216 -- in which the Weeping Angels lurked -- while Hurran also recorded on the sets for the security suite and the deactivated “god complex”. February 25th and 26th were spent back at the Seabank Hotel, with shooting now taking place on the staircases, in addition to further work in reception.

Sunday the 27th was a day off. On March 28th, cameras were rolling on the beauty salon set at Upper Boat; it was dubbed the Pasiphae Spa as an allusion to the mother of the Minotaur in Greek mythology. On March 1st, Amy and Rory's new home was actually a residence on Bute Esplanade in Cardiff Bay. This location differed from Whithouse's scripted description of an idyllic cottage, reflecting the fairytale theme which Moffat had woven throughout Amy and Rory's adventures. All of the outstanding filming for The God Complex then took place at Upper Boat. Sequences outside the salon were taped on March 3rd, followed by the other hotel bedrooms and shots of Lucy in the corridors on the 4th. Various inserts were recorded on March 14th and 15th. This left only the remaining security suite material and the concluding TARDIS scene, which were completed on March 18th.

As was now becoming increasingly common, the BBC granted permission for The God Complex to air in a fifty-minute timeslot, as opposed to the standard forty-five minutes. As a result, its broadcast on September 17th began at 7.10pm, five minutes earlier than the preceding Saturday. For the next two weeks, Doctor Who's lead-in would be a special edition of the cooking competition Celebrity MasterChef.

• Doctor Who Magazine Special Edition #31, 8th August 2012, “The God Complex” by Andrew Pixley, Panini UK Ltd.
• Doctor Who: The Complete History #69, 2018, “Story 222: The God Complex”, edited by John Ainsworth, Hachette Partworks Ltd.