Vastra, Jenny and Strax investigate the appearance of a tyrannosaurus rex in Whitehall, only to discover that it has accidentally accompanied Clara and the newly-regenerated Doctor. When the dinosaur suddenly combusts, the unstable Time Lord sets off on his own to investigate, little realising that a clockwork robot with half a face is stalking Victorian London. Meanwhile, Clara grapples with the profound change in the Doctor, until a mysterious message draws the pair back together. But when a confrontation with the Half-Face Man ensues, Clara must decide whether she can still trust the man she thought was her best friend.

Not long after Peter Capaldi agreed to become the Twelfth Doctor during the summer of 2013, he and Doctor Who executive producer Steven Moffat began to formulate their vision of the character. Moffat wanted to draw a contrast with Matt Smith's time as the Eleventh Doctor, which he had invested with a whimsical fairytale aesthetic. He saw Capaldi's early stories as an opportunity to establish a more serious take on the programme, which emphasised the Doctor's alien and sometimes unapproachable nature. For his part, Capaldi wanted to draw upon his own personality in crafting the Twelfth Doctor's character. Some consideration had been given to the Doctor speaking in an accent other than Capaldi's native Glaswegian brogue, but it was quickly agreed that the new Doctor's Scottish-ness would be a prominent feature of the incarnation.

The Twelfth Doctor's introductory adventure would lead off Season Thirty-Four. The first element Moffat wrote for his script was the Eleventh Doctor's cameo appearance, speaking to Clara from the events of his final story, The Time Of The Doctor, via the TARDIS telephone. It was originally thought that this would be Smith's final shot before leaving Doctor Who on October 5th, but the material was ultimately recorded one day early, on the standing TARDIS set at Roath Lock Studios in Cardiff.

So many returning characters would help to highlight the new Doctor's distinctive characteristics

Meanwhile, Moffat developed the opening sequence involving the tyrannosaur. He had not yet fleshed out his ideas for the rest of the narrative, but he anticipated being able to amend this scene to suit any direction the script ultimately took. For the Eleventh Doctor's debut, Moffat had effectively relaunched Doctor Who by writing The Eleventh Hour without any familiar elements beyond the TARDIS. A different tack was preferred for the Twelfth Doctor: not only would Jenna Coleman continue to play Clara Oswald, but other recognisable faces would be present in the form of the Paternoster Gang. This trio of Victorian investigators -- Madame Vastra, Jenny Flint and Commander Strax -- had most recently appeared in the Season Thirty-Three finale, The Name Of The Doctor. The inclusion of so many returning characters would not only serve to reassure the audience, but would also help to highlight the new Doctor's distinctive characteristics.

A first draft of the Season Thirty-Four premiere was completed on November 7th. At this stage, the obnoxious student in Clara's flashback was an unnamed schoolgirl. For his villains, Moffat decided to resurrect another established concept in the form of the Clockwork Robots, which he had created for 2006's The Girl In The Fireplace. Moffat imagined that the new Doctor would initially have no memory of his previous encounter with the Clockwork Robots; this was a device he recalled being employed occasionally in the American detective series Columbo, in which the title sleuth would seem nonplussed by references to his old cases.

Another nod to Doctor Who's past would be incorporated more obliquely: Moffat had decided to resurrect the Doctor's Time Lord arch-nemesis, the Master, who would make a series of brief appearances before the character's true identity was revealed in the season finale. A significant twist would be that the Master had regenerated into a female form; the groundwork for this possibility had been laid in Season Thirty-Two's The Doctor's Wife, which had acknowledged that a Time Lord could switch genders. The new incarnation would refer to herself as the Mistress, and so a cameo appearance at the end of the premiere would introduce her by the nickname “Misty”. At this stage, Moffat envisaged the character as a young woman.

As Moffat was refining his script, the celebrations surrounding Doctor Who's fiftieth anniversary reached a fever pitch. As part of the festivities, the children's magazine programme Blue Peter announced a tie-in competition -- the latest of several contests which had provided young viewers with an opportunity to contribute to Doctor Who. This time, the challenge was to design new sonic equipment for the Paternoster Gang, with a winning entry to be selected for each of Vastra, Jenny and Strax. The competition was announced to viewers on November 21st, two days before Capaldi made his surprise debut as the Twelfth Doctor with a cameo appearance in the anniversary special, The Day Of The Doctor.

Despite a 12-day deadline, the Blue Peter competition attracted 3600 entries

Although the Blue Peter competition had a tight twelve-day deadline, it still attracted three thousand six hundred entries. The winners were a sonic hatpin for Vastra, a sonic gauntlet for Jenny, and a sonic lorgnette -- spectacles mounted on a handle -- for Strax. The victorious designs were revealed on the Blue Peter Christmas special, broadcast on December 19th. One week later, on Christmas Day, Capaldi's tenure genuinely began with the Doctor's regeneration at the conclusion of The Time Of The Doctor. By now, the script for his introductory adventure had become known as Deep Breath.

Still to be determined were the clothes which Capaldi would wear as the Doctor, since his brief appearance in The Day Of The Doctor had been confined to a tight close-up of his eyes. Working with costume designer Howard Burden, it was agreed that the Twelfth Doctor would present a less colourful image than his predecessor; Capaldi thought in terms of the darker garments worn by the first three Doctors. The actor also wanted to avoid a signature accessory such as the Eleventh Doctor's bow tie, the Fifth Doctor's celery stick or the Fourth Doctor's scarf. The emerging goal was to develop an ensemble which simultaneously evoked multiple time periods and yet remained cohesive. For a while, it was thought that a cardigan would feature prominently, before Capaldi instead settled on a dark Crombie coat. Its striking red lining recalled the splash of colour provided by the Third Doctor's cape during Jon Pertwee's first season in 1970.

Deep Breath would be made as part of the first recording block for Season Thirty-Four, alongside the year's second episode, Into The Dalek. Assigned to direct was Ben Wheatley, a longtime Doctor Who fan who had been looking for an opportunity to make a programme that would appeal to his son. Wheatley would be working under a remodelled production team, following the departure of producer Marcus Wilson. His successors were Nikki Wilson, who had produced 2009's The Waters Of Mars as well as several seasons of the spin-off show The Sarah Jane Adventures, and Peter Bennett, who was reprising the role he had held on several episodes during Season Thirty-One, as well as the third season of Torchwood. Working closely with Wilson and Bennett would be another returning Doctor Who veteran: Tracie Simpson. Now the line producer, she had previously produced various stories in 2009 and 2010. Wilson and Simpson rejoined Doctor Who after filling the same roles on the medical drama Casualty, while Bennett had been producing the science-fantasy series Wizards Vs Aliens.

Filming for Season Thirty-Four got under way at the start of 2014, three months after The Time Of The Doctor had wrapped. On January 6th, Wheatley conducted various rehearsals and camera tests at Roath Lock, during which he captured the shot of the Thames after the Doctor's plunge. Recording for Deep Breath officially began on the 7th, which focussed on the opening sequence involving the tyrannosaur. The day began at The Maltings in Cardiff, before additional elements were filmed at Roath Lock. Neve McIntosh, Catrin Stewart and Dan Starkey all rejoined Doctor Who for the first time since completing The Name Of The Doctor in late 2012. January 8th to 10th were spent at Merthyr Mawr House in Bridgend, which once again posed as Vastra's house on Paternoster Row.

After the weekend, cast and crew returned to Merthyr Mawr House on January 13th and 14th. Part of the first day was also spent at Mount Stuart Square in Cardiff, filming shots of the mounted Doctor and Vastra's carriage making their way towards the immolated dinosaur. The rest of the week was confined to Roath Lock, starting on January 15th with the material on Westminster Bridge plus some effects shots. Wheatley then began taping scenes in the underground room hidden beneath Mancini's Family Restaurant on the 16th and 17th, prior to a rare three-day weekend. The remaining material in the underground room was completed on January 21st and 22nd. Part of the latter day was spent at Cardiff's Parc Thistle Hotel, which provided a dining area suitable for Mancini's; Wheatley's team remained there on the 23rd and 24th.

With work having begun on Into The Dalek, recording for Deep Breath now became more sporadic. On January 28th, Doctor Who returned to Queen Street in Cardiff, where the Ninth Doctor had brought companion Rose Tyler back to modern-day Earth in 2005's The End Of The World. The venue now hosted the Doctor and Clara's arrival in the present day, echoing the earlier sequence. The rest of the 28th was spent at Roath Lock capturing various inserts and effects shots. Wheatley also remounted some of the climactic confrontation between the Doctor and the Half-Face Man, since revisions to the dialogue meant that some of the footage from the Parc Thistle Hotel was no longer suitable. On the 29th, Alf and Elsie encountered the Half-Face Man on Victoria Place in Newport, where establishing shots of Madame Vastra's home were also recorded.

Courtney Woods was added to Deep Breath, taking the role of the anonymous schoolgirl in Clara's flashback

By now, the production team had become fond of Courtney Woods, the troublemaking Coal Hill School pupil developed by Gareth Roberts for The Caretaker later in the season. As such, it was decided that Courtney would be added to Deep Breath, taking the role of the anonymous schoolgirl in Clara's flashback. The part went to Ellis George -- her first in a television drama -- and she recorded her initial scene at Holton Primary School in Barry on February 1st. Later the same day, Wheatley taped several inserts for the season premiere at Roath Lock.

Various shots for Deep Breath went before the studio cameras from February 10th to 13th. The Doctor and Clara's abduction from Mancini's was captured on the first day, followed by their arrival in the underground chamber on the second day. The 11th also saw the completion of material in the shaft. The focus on the 12th was the revised TARDIS console room, which now incorporated several chalkboards and bookcases; the lighting had been adjusted so that the set was less starkly white. Wheatley also filmed some inserts which required green screen effects, while a second unit was at work on Bute Street in Cardiff, which served as the avenue outside Mancini's. More pick-up shots were on Wheatley's itinerary on the 13th, alongside the scene involving the Doctor and the tramp. The latter role was played by Brian Miller, who had been Dugdale in 1983's Snakedance and was the widower of Elisabeth Sladen, who had played companion Sarah Jane Smith. Miller's sequence was filmed at Insole Court in Llandaff.

On February 17th, Roath Lock hosted the Doctor's leap off the roof, plus green screen shots of the Time Lord hanging from a tree. Amongst various inserts taped in the studio on the 18th was the model shot of the TARDIS landing on the banks of the Thames. Further pick-up and model shots -- chiefly of the hot air balloon -- were captured at Roath Lock on March 28th. Meanwhile, the Master's new nickname had been changed from “Misty” to “Missy”, with Michelle Gomez cast as a more mature version of the character than Moffat had originally envisaged. Her cameo at the end of Deep Breath was taped on May 23rd, with Dyffryn Gardens in St Nicholas providing the idyllic setting. Finally, an insert of Vastra providing Jenny with oxygen in the underground room was taped at Roath Lock on June 27th.

Deep Breath had been allocated an eighty-minute timeslot -- nearly twice the length of a standard Doctor Who episode -- so very little editing was required in post-production. However, one crucial element which remained to be developed was the new title sequence. Looking for something innovative, Moffat had come across a showreel created by longtime fan Billy Hanshaw and posted to the YouTube video service in September 2013. It adopted a novel clockwork-inspired theme which Moffat thought might be ideal for his analytically-driven new Doctor, so Hanshaw was brought aboard to help the production team refine his concepts. Some aspects were dropped, such as the inclusion of the Seal of Rassilon introduced in 1976's The Deadly Assassin and a fob watch like the one which housed the Doctor's true personality in 2007's Human Nature / The Family Of Blood. The prominence of Capaldi's features was lessened, while the key colour was changed from purple to blue. Composer Murray Gold put together a new version of the Doctor Who theme from existing elements to accompany the overhauled titles.

August 7th marked the start of an unprecedented worldwide tour for Peter Capaldi and Jenna Coleman to promote Doctor Who

A promotional campaign for the forthcoming season began to kick into high gear in late June 2014, with the release of the first teaser trailer and the confirmation of the airdate for Deep Breath. Unfortunately, during July, it was revealed that both script and video material from Capaldi's first six episodes had been leaked from the Miami, Florida offices of the company providing translations for broadcasters in Latin America. The BBC implored fans to avoid the preliminary edits -- which were still extremely rough, lacking components such as finished visual effects -- and to refrain from posting spoilers from the scripts. August 7th marked the start of an unprecedented worldwide tour, with Capaldi and Coleman travelling to seven cities to promote Doctor Who. Starting in Cardiff, the duo made their way to London later the same day, and then flew to Seoul, South Korea on the 9th; Sydney, Australia on the 11th; New York on the 13th; Mexico City on the 15th; and finally Rio de Janeiro, Brazil on the 18th.

The rest of the world got to see the Season Thirty-Four premiere on August 23rd, with the television transmission accompanied by cinema screenings in a number of markets around the globe. On BBC One, Deep Breath aired at 7.50pm, between the celebrity acrobatics competition Tumble and the twenty-eighth season of Casualty. The programme effectively replaced Mrs Brown's Boys, which had concluded its third season the week before; the other Saturday evening programmes were rearranged to accommodate Doctor Who's earlier timeslot. The extended runtime of Deep Breath also meant that The National Lottery: Break The Safe was postponed for a week.

Attracting 9.2 million domestic viewers -- and over two million more on the BBC's iPlayer service -- Doctor Who was the United Kingdom's second-most-watched programme of the week, bested only by The Great British Bake Off. The festivities surrounding the show's golden anniversary may now have been a fading memory, but the public's enthusiasm for Doctor Who and its new leading man had hardly abated...

• The Doctor Who Companion -- The Twelfth Doctor: Volume One, June 2019, “Deep Breath” by Andrew Pixley, Panini UK Ltd.
• Doctor Who: The Complete History #76, 2015, “Story 242: Deep Breath”, edited by John Ainsworth, Hachette Partworks Ltd.