The TARDIS suddenly loses power, and the Doctor and Sarah emerge to find themselves trapped on the planet Exxilon. They meet a crew from Earth which has come to Exxilon seeking parrinium, which is needed to cure a virulent space plague. However, the humans are affected by the power drain, too -- as are the Daleks, who have also arrived in search of parrinium. The humans, the Daleks and the time travellers forge an uneasy alliance against the violent natives of Exxilon. But the Daleks are already plotting betrayal, and the Doctor is left with no choice but to venture into the Exxilons' forbidden city in search of answers.

During Doctor Who's tenth season, producer Barry Letts and script editor Terrance Dicks had positioned Planet Of The Daleks as the fourth of five stories. Letts was keen to repeat this schedule for Season Eleven; he was aware that the venerable monsters continued to attract considerable publicity, and could provide a mid-year ratings boost. In accordance with an agreement reached in 1971, Dalek creator Terry Nation was given the right of first refusal on writing the new serial; for the second year running, he agreed to provide the scripts himself. This suited Letts and Dicks, who intended to use only experienced Doctor Who writers for Season Eleven while much of their attention was consumed by their new science-fiction series, Moonbase 3.

Dicks suggested a narrative involving an intergalactic quest to find the cure for a space plague, and an advanced society which had reverted to barbarism. He wanted the Daleks to be less of a focus than in Planet Of The Daleks, and he also asked Nation to develop a more compelling female character than that serial's Rebec. When it was commissioned on March 23rd, 1973, Nation's storyline bore the working title “The Exilons”, in reference to the new aliens he had devised; their name was inspired by the healing “elixir” which was the heart of the adventure. This was subsequently amended to “The Exxilons”. Robert Holmes, who was trailing Dicks in preparation to become Doctor Who's new script editor, suggested that the connection between the aliens' name and the elixir was too obvious, and so the latter became the mineral parrinium.

Initially, the Daleks successfully absconded with the healing elixir

Nation's scripts were commissioned as Death To The Daleks on July 2nd. It may have been Holmes who suggested the new title, inspired by his dislike of Nation's famous monsters. Several modifications were made to avoid similarities with Planet Of The Daleks: the jungle-choked planet Exxilon became a rocky and barren world, while the humans were more securely established than the hunted Thals of Nation's previous story. Initially, the Exxilon city was powered by the elixir, and was destroyed when the Daleks successfully absconded with it; the humans worked with the Exxilons to reverse the decline of their civilisation, and were given more of the elixir in return. Nation conceived the Exxilons as being bat-like, and the subterranean Exxilon Gotal was originally called Jebal. Nation gave his key female character, Jill Tarrant, one of his favourite surnames, which he applied to various characters throughout his writing career.

The assignment to direct Death To The Daleks was originally offered to Paddy Russell, but she opted to work on the preceding story, Invasion Of The Dinosaurs. Michael Briant came aboard instead, having last directed The Green Death the year before. No new Daleks were constructed for the serial; Briant made use of the three surviving Sixties-era casings, bolstered by a trio of lesser-quality “goon” Daleks built for Planet Of The Daleks. Briant decided to repaint all six casings in a silver-and-black livery. He felt this echo of the Daleks' original monochrome appearance was more effective than the more colourful paint schemes employed over the last two years.

Location filming for Death To The Daleks spanned five days in November -- the 13th to the 16th, and the 19th. The only site used was the Amalgamated Roadstone Corporation Sand Pits at Gallows Hill near Binnegar, Dorset, which served as the surface of Exxilon. Briant had to rearrange his shooting schedule when Jon Pertwee's arrival was delayed by a severe attack of his chronic back pain. On the 16th, Elisabeth Sladen injured her ankle while running on the muddy ground; fortunately, she had largely completed her location material. Around this time, Barry Letts confirmed that he was leaving Doctor Who following the current recording block -- albeit not for Moonbase 3 as intended, which had been cancelled after attracting a small audience. In late November, BBC Head of Drama confirmed that Doctor Who would continue into a twelfth season, with Philip Hinchcliffe taking over as producer.

For much of the Pertwee era, the usual studio schedule had involved two consecutive recording days every fortnight -- latterly, a Monday and a Tuesday -- with each day typically devoted to a single episode. Compared to the Sixties method of taping one episode every week, this approach halved the wear and tear on the sets. Increasingly, directors had also been opting to tape each episode on a set-by-set basis, rather than in strict story order, to make the recording day more productive. Briant elected to take this notion one step further: he decided to arrange each studio block so that all of the scenes using a given set were recorded on a single day, regardless of the episode in which they appeared. Letts had done something similar for the previous season's Carnival Of Monsters, albeit due to the rigid division of that serial between two settings with distinct casts of characters. Furthermore, instead of holding camera rehearsals each afternoon with taping in the evenings, Briant used the entirety of the Monday for camera rehearsals and confined the actual recording to the Tuesday.

Under this arrangement, the first studio session took place on December 3rd and 4th at BBC Television Centre Studio 4 in White City, London. Unfortunately, Briant's efforts were undermined when several props and set elements went missing on the Monday, limiting the extent of the rehearsals. This placed additional demands on the lengthy recording schedule for the Tuesday, which the cast consequently found exhausting. The situation was exacerbated by Pertwee's increasingly disinterested attitude towards Doctor Who, and his disdain for the Daleks. Sets in use included those for the TARDIS, the sand dunes, the humans' dome, the exterior of the Dalek ship, the approach to the Exxilon city, the temple and the cell. The second studio block was held on December 17th and 18th in TC3. It covered material inside the Dalek ship, in the tunnels, and within the city.

In editing, it was realised that Episode Three was running short while Episode Four was very long. As a result, material from the start of the concluding installment was used to form a new cliffhanger. Originally, Episode Three ended when the Daleks emerged into the maze room. It now continued to the Doctor and Bellal reaching the trapped floor pattern, and ended on the Doctor's warning to freeze.

The individuals who had helped define Jon Pertwee's era were moving on to pastures new

By the time the Doctor Who team began their Christmas holidays, Pertwee had made a decision about his future on the programme. Many of the actors he had bonded with during his time on the series had either left the show, or were gradually being phased out, including Katy Manning (Jo Grant), Nicholas Courtney (Brigadier Lethbridge-Stewart), John Levene (Sergeant Benton) and Richard Franklin (Captain Yates). Furthermore, Pertwee had been badly shaken by the accidental death of Roger Delgado (the Master) during the summer. With Dicks already in the process of stepping down as script editor, and now Letts announcing that his departure was imminent, Pertwee was aware that the individuals who had helped define his era were moving on to pastures new.

These factors, combined with his mounting boredom and chronic back pain, convinced Pertwee that it was time for him to leave Doctor Who as well. When Shaun Sutton telephoned him to persuade him to change his mind, the series star responded with a request for a significant pay raise; it was immediately denied. Pertwee's departure was announced to the press on February 8th, 1974.

• Doctor Who Magazine #278, 2nd June 1999, “Archive: Death To The Daleks” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #2, 5th September 2002, “The Show Must Go On” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #21, 2017, “Story 72: Death To The Daleks”, edited by John Ainsworth, Hachette Partworks Ltd.
• Doctor Who: The Handbook: The Third Doctor by David J Howe and Stephen James Walker (1996), Virgin Publishing.
• Doctor Who: The Seventies by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing.