Development "The Well" was written by
Russell T Davies, the
Doctor Who showrunner, and Sharma Angel-Walfall, one of the four guest writers of the series. Prior to being hired, Angel-Walfall had been working with
Jane Tranter on another
Bad Wolf production, and it was Tranter who suggested Angel-Walfall to Davies. Working with Davies in the television industry had been a dream of Angell-Walfall's ever since she saw him speak when she was a child. Ahead of his initial interview with her, Davies read a "supernatural-horror-type drama" script she had written, and decided to use it as a basis for the tone of the story. As they worked on the episode, they engaged in a lot of "back-and-forth" about it, working closely with each other to develop it. When teasing the series, Davies said that one of the previous episodes contained an "unexpected sequel". Many theories arose that "The Well" would be that episode, with assumptions made that it could be a follow-up to a number of episodes, including "
The Impossible Planet" / "
The Satan Pit" (2006), "
Midnight" (2008), "
The Waters of Mars" (2009), and "
Wild Blue Yonder" (2023). It ultimately ended up being a successor to "Midnight", with the story taking place on the same planet 400,000 years later. The script was originally intended to feature Nigerian spirits known as the
Orishas as the primary antagonists, which series star
Ncuti Gatwa had publicly named as a "dream storyline" of his shortly after being cast. After the writers felt they could not depict the Orishas with an appropriate level of respect, however, the episode was converted into a direct sequel to "Midnight", largely because Davies felt that the actions in the original script aligned with the behaviour of the Midnight Entity in its original appearance. Originally, Davies had considered titling the episode "The Thirteen" because thirteen people come to planet Midnight.
Casting portrayed Aliss Fenly. The episode stars
Ncuti Gatwa as the
fifteenth incarnation of
The Doctor and
Varada Sethu as his
companion,
Belinda Chandra. Guest character Aliss Fenly is portrayed by deaf actress
Rose Ayling-Ellis, who communicates using
British Sign Language (BSL). She was excited to appear in the series, saying it was on her
bucket list. Ayling-Ellis and Gatwa used BSL to communicate with each other.
Christopher Chung also guest stars in the episode as Cassio. Chung previously auditioned for two other
Doctor Who episodes prior to being cast in the programme, including "
Knock Knock" (2017).
Paul Kasey portrayed the Midnight Entity (credited as "It Has No Name"), which was never seen in "Midnight". Kasey filmed the scenes with Ayling-Ellis right behind her in order to convey the feeling of the creature that Aliss would feel in the episode. an enigmatic recurring character featured as part of the series' ongoing story arc. The remainder of the guest cast included
Caoilfhionn Dunne and
Bethany Antonia as Shaya Costallion and Mo Gilliben, respectively.
Filming and music took place at
Pant-y-Ffynnon Quarry. Before production commenced, the actors portraying troopers attended a
boot camp on 29 January 2024, taught by a former member of the military. A deaf-awareness course was also held for the cast and crew, and a consultant was on set to ensure authenticity while the characters were signing. The episode was filmed in the series' third production block, along with the preceding episode, "
Lux". It was directed by
Amanda Brotchie and the main set was constructed on Stage 6 at Wolf Studios Wales.
Location filming took place at
Pant-y-Ffynnon Quarry in
Bridgend Wales on 1 February 2024. Some of the recording sessions occurred as late as 2:00 a.m. in subzero temperatures. The space suit helmets also proved challenging for the actors by misting up and causing issues in breathing and hearing, even though timing of the filming was done to avoid the misting. == Broadcast and reception ==