When the Doctor returns to Leadworth to update Amy and Rory on his search for their daughter, Melody, their friend Mels shows up too. She forces the Doctor to take them to 1938 Berlin so she can kill Adolf Hitler, but her plans go awry due to the presence of the Teselecta, a shapeshifting Justice Department Vehicle from the future. Although she's mortally wounded, Mels doesn't die. Revealing that she's really Melody Pond, she regenerates... into the woman whom the astonished time travellers know as River Song. But little do they realise, Melody has been brainwashed by the Silence -- into murdering the Doctor.

Unlike any season of Doctor Who before it, Season Thirty-Two was divided into two halves, split across the summer months. The first half would climax with episode seven, A Good Man Goes To War, and end on a cliffhanger as the Doctor departed to search for Amy and Rory's missing daughter, Melody Pond. Three months later, viewers would return to the storyline with episode eight; as such, it would effectively serve as the year's second premiere-type adventure. Executive producer Steven Moffat needed to devise a script which would draw viewers back to Doctor Who after a twelve-week break, while also progressing the narrative surrounding baby Melody's abduction. Furthermore, he was keen to write a story which would be tonally different from The Impossible Astronaut, the year's dark and ominous debut episode.

This led Moffat to the notion of an adventure which would promise an encounter with infamous Nazi leader Adolf Hitler. Elected Chancellor of Germany in 1933, Hitler's aggressive posturing steadily drove his country towards military action. In 1939, his decision to annex Poland -- and later other European nations -- sparked the Second World War. The atrocities committed by the Nazis and their Axis allies, including the campaigns of ethnic cleansing which Hitler waged against Jewish civilians and other minorities, made him the most reviled figure of the twentieth century. Moffat believed that a form of modern revenge against the Führer was to make him a figure of mockery and belittlement; as such, the Doctor's encounter with Hitler would become a comedic sideshow. This approach was inspired by the 1989 film Indiana Jones and The Last Crusade, in which the eponymous archaeologist inadvertently found himself collecting Hitler's autograph.

Steven Moffat wanted the narrative's focus to be on the relationship between Amy, Rory and River

Moffat's script consequently gained the intentionally lurid title Let's Kill Hitler. However, the writer wanted the narrative's true focus to be on the relationship between Amy, Rory and River Song, who had been unmasked as a future version of Melody in A Good Man Goes To War. In particular, the revelation that Amy and Rory's childhood friend Mels was another incarnation of Melody/River was intended to temper the darker implications of the baby's abduction, since Amy and Rory would now be shown to have played an integral role in their daughter's formative years.

Moffat was writing Let's Kill Hitler by the middle of January 2011. The inclusion of Professor Candy and Luna University alluded to his short story “Continuity Errors” from Virgin Publishing's 1996 anthology Decalog 3: Consequences. As production approached, one element which changed considerably was the appearance of the Anti-Bodies which provided security aboard the Teselecta. Moffat originally envisaged them as humanoid robots with featureless chrome heads. However, it was eventually felt that this design hewed too closely to the look of the Handbots from episode ten, The Girl Who Waited. As such, the Anti-Bodies instead became floating, tentacular automatons.

Let's Kill Hitler was made on its own as Season Thirty-Two's eighth recording block (although it was formally dubbed “Block Seven-A”). The director was Richard Senior, who had recently shot the mini-adventure Space / Time for the 2011 Red Nose Day fundraiser, and would represent his first opportunity to direct a full television episode. Amongst those who unsuccessfully auditioned for the role of Mels was Jenna-Louise Coleman; less than a year later, she would win the role of companion Clara Oswald. The part ultimately went to Nina Toussaint-White, who had spent 2009 as a regular on EastEnders. By casting a person of colour as Mels, the production team definitively established that race was another characteristic which could change via the process of regeneration. Indeed, Moffat had previously explored the possibility of selecting a non-white actor to portray the Eleventh Doctor. Meanwhile, Caitlin Blackwood would be appearing in Doctor Who for the fourth and final time as the young Amelia Pond.

The first several days of production on Let's Kill Hitler took place at Doctor Who's regular studio facilities in Upper Boat. On March 22nd, Senior recorded the scenes of Amy, Rory and Mels in Amy's bedroom and outside the principal's office. More flashbacks -- this time at the police cells -- were on the schedule for the 24th, along with work on the TARDIS set. Sequences on the bridge of the Teselecta were filmed on March 25th and 28th, straddling the weekend. Material in Hitler's office was taped on the 29th and the 30th. Senior's team finally ventured outside the studio on March 31st and April 1st, when material in the Hotel Adlon's dining room was recorded at the Temple of Peace in Cardiff. A shot of Zimmerman approaching the German Chancellery was also captured there on the first day. On April 2nd, Brangwyn Hall in Swansea offered spaces suitable for the Chancellery courtyard and the corridor inside; across the street, the Guildhall posed as the hotel exterior.

After a day off on the 3rd, it was back to Upper Boat on April 4th. Senior's itinerary involved further sequences in the TARDIS, and a start on those which took place in the bridge, lift and gantry area of the Teselecta. The 5th saw a reprise of the work in Hitler's office, some of which had been delayed because of the complexity of achieving the TARDIS crashing through the windows. Work on this set wrapped up on the 6th, when Senior also recorded scenes in River's hospital room, the TARDIS and the Teselecta gantry, as well as several inserts. Filming on April 7th began at Cyfarthfa Castle High School in Merthyr Tydfil, for the playground and classroom flashbacks. Material in Zimmerman's office was then taped at Upper Boat before Senior wrapped up the day at Hensol Castle in Hensol, for the concluding sequence at Luna University.

There was a hiatus lasting 2½ months before the final location shoot for Let's Kill Hitler

Upper Boat was the venue for a variety of pick-up shots on April 16th, 18th and 19th. On April 25th, the prequel for Let's Kill Hitler was filmed on the standing TARDIS set. Directed by Steve Hughes -- who had handled the season's penultimate episode, Closing Time -- it depicted the Doctor listening to a voicemail message from Amy, and functioned as a recap of the circumstances surrounding his search for Melody Pond. Effects work against green and blue screens then took place at Upper Boat on April 30th. Unusually, there followed a hiatus lasting two and a half months before the final location shoot for Let's Kill Hitler. The work in question was the opening sequence in the cornfield, and it would take until midsummer before the crops had reached an appropriate height. As such, this material was finally filmed on July 10th and 11th at Penmark, drawing the production of Season Thirty-Two to a belated close.

In the meantime, the Controller of Programmes for BBC One, Jay Hunt, announced on June 14th that Doctor Who had been renewed for its thirty-third season. However, he cautioned that the regular allotment of thirteen episodes would not air in 2012, with a portion instead held over to 2013. Hunt attributed this scheduling decision to the fact that Moffat was also developing the second season of Sherlock, the popular mystery series he was showrunning with Mark Gatiss. Moffat himself, however, was quick to contradict Hunt, insisting that there was no relationship between the production of Sherlock and the limited number of Doctor Who episodes which would be transmitted in 2012.

A second announcement concerning the future of Doctor Who came on July 7th, when it was revealed that executive producer Beth Willis was about to leave the programme to return to her previous post at Kudos Film and Television. With Piers Wenger's departure also imminent, this would leave Moffat as the last of the three executive producers who had ushered in Matt Smith's time as the Doctor. Two weeks later, on July 21st, Caroline Skinner was announced as the successor to Willis and Wenger. A former script editor who had recently produced Five Days and the dark fantasy series The Fades, Skinner would join the Doctor Who team with the 2011 Christmas special, The Doctor, The Widow And The Wardrobe.

On August 15th, the prequel to Let's Kill Hitler was released online; it ran to one hundred and sixteen seconds. Given the episode's premiere status, permission was granted for Let's Kill Hitler to air in a fifty-minute timeslot, five minutes longer than usual. It was scheduled at 7.10pm on August 27th, and aired between a pair of game shows: the first of two special editions of Total Wipeout, and The National Lottery: Secret Fortune. The eighty-four days which had elapsed since the broadcast of A Good Man Goes To War marked the longest break within a single Doctor Who season to date. It also meant that, for the first time since 1989, the programme would still be on the air as the long summer days began to give way to the darker evenings of autumn...

• Doctor Who Magazine Special Edition #30, 21st March 2012, “Let's Kill Hitler” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #68, 2017, “Story 219: Let's Kill Hitler”, edited by Mark Wright, Hachette Partworks Ltd.