Rigsy summons the Doctor and Clara for help after waking up with no memory of the previous day, and a tattoo on his neck which is inexorably counting down. Discovering that Rigsy has recently had significant contact with extraterrestrial life, the Doctor searches for a hidden place in the heart of London. He finds a street which serves as a refuge for aliens, where the self-styled mayor is none other than Ashildr. She keeps the peace via a Quantum Shade: an unstoppable killer which manifests as an eerie raven. Rigsy stands accused of murder and, unless the Doctor can unravel the mystery, someone will inevitably face the raven.

By the early 2010s, Doctor Who had already played a major role in Sarah Dollard's life. She had become a fan of the series while growing up in her native Australia, and the ambition of its twenty-first-century revival had helped inspire her decision to immigrate to the United Kingdom, where she could work in a television landscape with the capacity to produce programmes on such a scale. Having established her credentials in Britain, Dollard won an invitation in July 2014 to meet with Doctor Who script executive Lindsay Alford. Dollard proposed an adventure about a trap street: a fictitious or misrepresented street included by a cartographer on a map as a watermark, allowing the identification of unauthorised copies. She suggested a narrative in which the Doctor discovered that a trap street actually marked the location of a hidden place where people lived in secret.

Doctor Who executive producer Steven Moffat was excited by the notion; he imagined that it might inspire children to explore their own neighbourhoods, looking for places that had previously gone unnoticed. Moffat suggested that the residents of the trap street should be alien refugees, one of whom had been murdered. This approach appealed to Dollard, whose parents were avid mystery buffs. It was soon decided that an established character should be used to draw the Doctor and Clara into the story, with Alford suggesting the graffiti artist Rigsy whom Jamie Mathieson had created for Season Thirty-Four's Flatline.

The mayor was originally an officious insectoid alien, assisted by a Sontaran named Skarn

Dollard was commissioned to write “Trap Street” in late January 2015, and she completed a first draft of the script around the middle of February. At this stage, the adventure opened with Rigsy summoning the Doctor and Clara away from a poker game which also featured Top Gear host Jeremy Clarkson, American frontiersman “Wild Bill” Hickok, and Pride And Prejudice author Jane Austen. Access to the trap street was granted via a brick wall: any door sketched upon it became real. The mayor was an officious insectoid alien, assisted by a Sontaran named Skarn; there were also Adipose (from 2008's Partners In Crime) living in the refuge, which was said to have existed for one hundred and eight years.

The Doctor and Clara investigated the murder of Anah the Janus, whose species took its name from the Roman god of time and transitions, a figure often depicted as having a face on both the front and back of his head. In the process, they discovered that Skarn was fomenting war with humanity, terrifying the refugees with grotesque fictions. He had killed Anah because she had learned of his plans via her ability to see through time. The Mayor refused to believe that Skarn was the murderer until Anahson -- actually called Pae -- revealed that she was also a female Janus and confirmed the truth about her mother's death. With seconds to spare, the Mayor removed the chronolock which would have compelled the Quantum Shade to kill Rigsy.

To this point, Moffat's inclination had been to place “Trap Street” either immediately before or after The Zygon Invasion / The Zygon Inversion, as either the seventh or ninth episode of Season Thirty-Five. However, Dollard's initial draft was so well-received that he decided it should air tenth, immediately before the two linked episodes which would close the run. To propel events towards the year's climax, a pair of significant changes would have to be made to the narrative.

First, Moffat wanted to bring back the immortal Ashildr, who would be introduced in episode five, The Girl Who Died, and then encounter the Doctor again in episode six, The Woman Who Lived. He anticipated a final meeting between the Doctor and Ashildr in the season finale -- ultimately Hell Bent -- and he was keen for her to appear again in the interim. As such, it was agreed that Ashildr would replace the insectoid alien as the trap street's mayor.

Clara embraced a reckless zeal for her adventures that would ultimately lead to her death

Second, it had been known from the outset that Jenna Coleman would be leaving Doctor Who after Season Thirty-Five. Indeed, she had originally planned to depart in the Season Thirty-Four finale, Death In Heaven, and again in the 2014 holiday special, Last Christmas, but she had been tempted back by the prospect of an additional year acting opposite Peter Capaldi. This time, Moffat had structured the season to depict Clara acting in a manner that was increasingly Doctor-like, embracing a reckless zeal for her adventures that would ultimately lead to her death. Although the season finale seemed to be the natural place for Clara to meet her end, Moffat now decided to shock audiences by positioning the event during the year's third-last episode. Consequently, Clara would wind up the victim of the Quantum Shade after taking the chronolock from Rigsy, because she hadn't considered the possibility that a solution might not be found in time.

The resulting second draft of “Trap Street” was prepared by the end of March. Dollard had now deemphasised the murder-mystery aspects of the narrative, with Anah revealed to be in stasis rather than dead. Skarn was omitted, while comedian Russell Brand took Jeremy Clarkson's place in the opening segment, which was later dropped altogether. As Clara bade farewell to her friends, Rigsy revealed that his daughter Lucy's middle name was Clara. To reduce the requirement for effects and prosthetics, Dollard significantly curtailed the amount of screen time during which the various aliens would appear in their true forms.

“Trap Street” was initially paired with episode nine, Sleep No More, as the season's fifth recording block under director Justin Molotnikov. In late April, however, it was decided that the two stories would be split up. They would now be made on either side of Block Six, which consisted solely of the highly-unusual episode eleven, Heaven Sent, a one-hander featuring only the Doctor and a mute monster. Initially, “Trap Street” was deferred to Block Seven but, by the middle of May, it had taken the place of Sleep No More as Block Five. The adventure would be produced by Nikki Wilson, who was returning from maternity leave.

Filming on “Trap Street” got under way on the standing TARDIS set at Roath Lock Studios in Cardiff. Work there spanned June 8th and 9th, with part of the latter day spent on the studio backlot shooting the effects sequences of Clara dangling above London. Molotnikov's team took to the roads of Cardiff on the 10th for the scenes of the Doctor, Clara and Rigsy looking for the trap street. The trio split up near the statue of John Batchelor on The Hayes and proceeded along nearby thoroughfares before their search culminated on Westgate Street, at its intersection with Park Street. Recording on June 11th began at Cardiff University, where the Main Building served as the Great British Library, and the TARDIS materialised near the School of Biosciences. Material in Lucy's nursery was shot that afternoon at Roath Lock. Cast and crew remained in the studio on the 12th to make a start on scenes in the infirmary.

The remaining infirmary material was completed following the weekend, on June 15th and 16th. The latter day then saw Molotnikov move over to the extensive set for the trap street itself, where Coleman performed Clara's death scene. Action on the street remained the focus for the rest of the week, through to June 19th, when the coda of Rigsy painting Clara's memorial was also shot on the backlot for the Welsh-language soap opera Pobol y Cwm. This was originally a longer sequence, with his fiancee Jen and baby Lucy watching as the mural came together.

There were more scenes on the trap street to be filmed after a weekend off, with cameras rolling there from June 22nd to 25th. In addition, part of the 23rd was spent on events in Anah's home, several inserts were shot on the 24th, and the scene in Rigsy's bathroom was taped on the 25th. The latter day also saw Channel View Flats in Cardiff pose as the exterior of Rigsy's apartment block. Finally, pick-up shots of the stasis pod keyhole were completed at Roath Lock on July 3rd.

Dialogue deleted in editing would have revealed Rigsy's real name to be Christopher Riggins. Also dropped was an exchange between Ashildr and the Doctor before he was teleported away, in which the mayor promised not to wipe Rigsy's memory again so that he could recall what had happened to Clara. During a September 18th interview on BBC Radio One's Breakfast Show, Coleman confirmed that Season Thirty-Five would be her last on Doctor Who. Around the same time, the title of Dollard's story was changed to Face The Raven. It aired on November 21st in an 8.10pm timeslot, as Doctor Who continued to bounce around the quarter-hour.

• Doctor Who: The Complete History #83, 2018, “Story 260: Face The Raven”, edited by John Ainsworth, Hachette Partworks Ltd.