The Doctor, Amy and Rory are confronted by the enigmatic Dream Lord, who forces them to oscillate back and forth between two different realities. In one, they're stranded aboard a crippled TARDIS, being inexorably drawn towards a cold star. In the other, the Doctor is visiting Rory and a pregnant Amy in Leadworth when they discover that the residents of a nursing home have become the hosts of alien parasites called the Eknodines. In both cases, the trio faces a mortal peril... but they must first deduce which is the true reality, or become trapped in the dream for the little time that remains to them.

In 1996, Steven Moffat met television producer Sue Vertue, whom he would marry two years later. Vertue's mother was Beryl Vertue, who had worked as an agent -- including for Terry Nation, the creator of the Daleks -- and as a producer herself. One of the programmes overseen by the elder Vertue was Men Behaving Badly, a popular Nineties sitcom adapted by Simon Nye from his 1989 novel of the same name. As a result, Moffat and Nye came to know each other, including the fact that both were longtime admirers of Doctor Who. When Moffat became the executive producer of Doctor Who in 2008, the two men discussed the possibility of Nye writing an episode of the show. Although his workload prevented him from immediately accepting the offer, Nye was eventually able to confirm his availability during 2009.

At this stage, many elements of Doctor Who's thirty-first season had come into focus. One of the remaining gaps was the seventh episode, which would fall between the addition of Rory Williams to the TARDIS crew in The Vampires Of Venice and his erasure from time at the conclusion of The Hungry Earth / Cold Blood. It had previously been occupied by Neil Gaiman's The Doctor's Wife, which was moved to the eleventh slot and finally postponed to Season Thirty-Two. Since Nye was skilled at writing interpersonal relationships, Moffat asked him to devise a story which would examine the complex interplay between the Doctor, Amy and Rory. The closing seconds of the season premiere, The Eleventh Hour, had revealed that Amy and Rory were engaged to be married. Nonetheless, Amy ran away in the TARDIS on the night before the wedding, and later exhibited a romantic infatuation with the Doctor in Flesh And Stone. As a result, the Doctor invited Rory to join them at the start of The Vampires Of Venice, and it would now be Nye's job to firmly establish that Amy's love for Rory was genuine and deeply-felt.

Simon Nye would require only a small guest cast and confine much of the action to the standing TARDIS set

Nye's adventure was also conceived with an eye on Doctor Who's budget, since it would be made towards the end of the year when funds were often running low. It was agreed that his starting point would be the way people in the process of waking up sometimes struggled to differentiate between the real world and the world of dreams. Such a narrative would permit Nye to require only a small guest cast, and confine much of the action to the standing TARDIS set. In the Eknodines, he conceived monsters which could be straightforwardly realised -- although there was some indecision as to whether it should be one eyeball or two which would emerge from the mouths of the possessed senior citizens.

Nye's script, entitled “The Dream Lord”, was scheduled to be made as part of Block Seven -- the final production block for Season Thirty-One -- alongside The Lodger. The director was Catherine Morshead, who had previously directed Nye's adaptation of The Railway Children. Given the nature of the episode, Morshead spent more time than usual recording on the TARDIS set at Doctor Who's regular studio home in Upper Boat. Indeed, the first three days of work -- February 18th to 20th, 2010 -- were all spent there. Early drafts of “The Dream Lord” had situated some of this material in the time machine's corridors, but it was ultimately decided that they would be an unnecessary expense.

Following a day off on Sunday the 21st, more recording in the TARDIS took place at Upper Boat on February 22nd. By now, the console room had been given a frozen appearance using a spray of wax and plastic. Whereas Llandaff in Cardiff had posed as Leadworth for The Eleventh Hour, the main filming location for “The Dream Lord” was the village of Skenfrith. As such, Nye's script was amended to note that the future versions of Amy and Rory lived in “Upper” Leadworth. Cameras rolled there from February 23rd to 25th, including work at Skenfrith Castle, an eleventh-century edifice which had been derelict for almost five hundred years. The material at the ruins which the children visited on their school trip was originally set in a primary school playground. Morshead's team wrapped up the week at Keepers Cottage in Llanblethian, which served as Amy and Rory's home in Upper Leadworth.

After the weekend, work at Keepers Cottage continued on March 1st and 2nd. On the 3rd, the Doctor tried to evade the Eknodines at Alan Young Butchers in Llantwit Major. The next filming for “The Dream Lord” took place on March 6th at Lanelay Hall in Pontyclun, which was dressed as the nursing home. It was back to Upper Boat on the 9th for more scenes in the TARDIS, after which Morshead focussed her attention on The Lodger. Work on “The Dream Lord” finally resumed on March 19th, which initially took cast and crew to Caerphilly. There, shots of the camper van in motion and Rory on his bicycle were captured along Eglwysilan Road. The day ended back on the TARDIS set at Upper Boat, with Morshead also seizing the opportunity to tape several inserts. The remaining TARDIS material was filmed in the studio on March 20th, alongside various effects shots. This was the last day of production on Season Thirty-One.

It was around this point that the episode was renamed Amy's Choice. The new title echoed that of William Styron's 1979 novel Sophie's Choice -- as well as its 1982 film adaptation starring Meryl Streep -- about a Jewish woman at a Nazi concentration camp who was forced to choose which of her two children would be executed. Amy's Choice was broadcast on May 15th; after its unusually early timeslot the week before, Doctor Who was back to the more typical start time of 6.25pm.

• Doctor Who Magazine Special Edition #27, 16th March 2011, “Amy's Choice” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #64, 2016, “Story 208: Amy's Choice”, edited by Mark Wright, Hachette Partworks Ltd.