The Doctor and Clara awaken to find themselves in a room with a shapeshifter named Saibra and a hacker called Psi. Their short-term memories have been wiped, and they know only that they have been assembled by a mysterious Architect to break into the intergalactic Bank of Karabraxos. Despite having little understanding of their goal, they agree to work together to confront the Bank's sophisticated and deadly anti-intrusion measures. The most formidable of all is the Teller, a creature controlled by the icy head of security, Ms Delphox. It has the power to sense the guilty -- and liquefy their brains.

Long before he began planning Doctor Who's thirty-fourth season, executive producer Steven Moffat had considered the possibility of an adventure which combined time travel with a heist scenario. Originally popularised in the middle of the twentieth century, the caper genre had enjoyed a resurgence in recent years spurred by updated versions of the original classics, such as Ocean's 11 (1960; remade in 2001) and The Italian Job (1969; remade in 2003). Having struggled to flesh out a detailed approach to the story, in 2013 Moffat asked Steve Thompson to develop a storyline in which the Doctor and Clara helped rob an extraterrestrial bank. Thompson had recently written Season Thirty-Three's Journey To The Centre Of The TARDIS, and he had demonstrated his skill with complex, puzzle-box plots while working with Moffat on the mystery series Sherlock.

Thompson knew that a heist narrative would invite comparisons to some of the most popular examples of the genre. As such, he tried to anticipate the plot expectations that would accompany such a narrative, including having the Doctor and Clara form part of a team of operatives. One of their accomplices would be a master of disguise, while another would reflect the trend in modern caper films of featuring a character who was a technological savant. Meanwhile, Ms Delphox was inspired by Zachary Garber, the police lieutenant played by Walter Matthau in 1974's The Taking Of Pelham One Two Three, who matched wits with a team of criminals holding the passengers hostage aboard a train car.

The story began with the Doctor and his team dropped onto the bank from a space shuttle

By late November, the adventure was called Time Heist. At this stage, the shapeshifter's name was spelt Sabra rather than Saibra, and she gained her abilities by virtue of being half-Zygon. The Teller was confined to a wheelchair, and was more insectoid in appearance. The bank was known as Fortuna-Vega; its director was Victor Karabraxos III, and the notion of Ms Delphox being a clone had not yet been introduced. The story did not begin with the Doctor and his team already at the bank, but instead saw them dropped onto the premises from a space shuttle on autopilot. A key plot point was then Clara's loss of the communicator via which the Architect was meant to deliver his instructions, forcing the Doctor to extrapolate the scheme based on the briefcases which the Architect had planted for them to find.

As Time Heist was refined in late 2013 and early 2014, various notions were incorporated and then discarded. In one draft, the script opened with vignettes which introduced Saibra and Psi and their respective talents. With the Zygon aspect of Saibra's background having been dropped, she was briefly the result of a laboratory experiment before becoming a mutant. At one point, Clara was to use thoughts of her boyfriend, Danny Pink, as a defence against the Teller. With Moffat having made significant contributions to both the story's premise and the final form of the script, it was agreed that he and Thompson would share the writing credit; this would now become an increasingly common practice to recognise Moffat's involvement in the writing process.

Although Time Heist was intended to be the fifth story broadcast during Season Thirty-Four, it was amongst the second pair of episodes to go before the cameras. As part of Block Two, it would join Listen under director Douglas Mackinnon. Production began on March 3rd, when scenes on the bank floor were staged at Roath Lock Studios in Cardiff. The Teller costume made its debut on this day; worn by actor Ross Mullan, it most prominently featured two tentacular eyes which were realised as a remote-controlled prosthetic. The 4th saw TARDIS material taped at Roath Lock, alongside the phone call made by the aged Director Karabraxos and crowd multiplication shots on the bank floor. The chief location for Time Heist was an unoccupied factory in Bridgend which had previously housed Kimball Electronics. Sequences in the basement were taped there on March 5th, followed by those in the cells holding the Teller's victims and various corridors on the 6th. Work in the vault and the adjoining hallway began on March 7th, while the Doctor left the briefcase at the security doors.

After the weekend, it was back to the Kimball Electronics factory from March 10th to 12th. In addition to more corridor scenes, Mackinnon shot material in the vault on the first day, in Ms Delphox's office on the middle day, and in the Teller's lair on the last day. Work on the 13th began at the Oval Basin Events Arena in Cardiff Bay, where the bar provided the venue for the flashbacks of the Doctor meeting Saibra, Psi and Porrima. Cast and crew then relocated to the nearby Roald Dahl Plass for the scene outside the bank with Saibra disguised as Porrima. The latter part of the day was spent on the set for Ms Karabraxos' private office, erected at Roath Lock; this work continued to March 14th.

Another weekend off preceded a studio day on March 17th. It concentrated on sequences in the safety deposit booth, alongside Psi's farewell on the TARDIS set. Work on the 18th began at Cardiff University's Hadyn Ellis Medical Research Facility, which offered space suitable for the security screening area. The planet which would become the new home for the Teller and its mate was then created with the help of green screens at nearby Bute Park. Scenes in Clara's apartment were taped at Roath Lock on March 19th. Principal photography on Time Heist concluded on the 21st, when material in the service level was recorded at the Uskmouth Power Station in Newport. A small amount of material remained outstanding, and was completed at Roath Lock. The footage of the Doctor masquerading as the Architect was filmed on March 24th alongside further TARDIS sequences and various inserts, while an additional pick-up shot of a briefcase was captured on May 6th.

Psi's compilation of thieves and villains included numerous references to Doctor Who's history. Amongst the hoodlums were a Sensorite (from 1964's The Sensorites), an Ice Warrior (introduced in 1967's The Ice Warriors), a Terileptil (from 1982's The Visitation), a Slitheen (introduced in 2005's Aliens Of London / World War Three), and Kahler-Tek (a cyborg from 2012's A Town Called Mercy). Four of the images hailed from Doctor Who spin-off series: a Weevil (introduced in Everything Changes, the 2006 premiere episode of Torchwood), the Trickster (introduced in Whatever Happened To Sarah Jane?, a 2007 episode of The Sarah Jane Adventures), Captain John Hart (a rogue Time Agent introduced in the 2008 Torchwood episode Kiss Kiss, Bang Bang), and Androvax the Veil (introduced in Prisoner Of The Judoon, a 2009 episode of The Sarah Jane Adventures). Most obscure was Abslom Daak, Dalek Killer. He had never before appeared on television, but had been a recurring character in various Doctor Who spin-off media since 1980, starting with comic strips in Doctor Who Weekly.

Doctor Who was again allocated a fifty-minute timeslot for the broadcast of Time Heist on September 20th. With Tumble having ended its season the week before, Pointless Celebrities served as the lead-in for the Karabraxos caper.

• The Doctor Who Companion -- The Twelfth Doctor: Volume Two, October 2019, “Time Heist” by Andrew Pixley, Panini UK Ltd.
• Doctor Who: The Complete History #77, 2016, “Story 246: Time Heist”, edited by Mark Wright, Hachette Partworks Ltd.