Fourth Season finale The Evil of the Daleks was originally intended as the last appearance of the Daleks in Doctor Who.
Their creator, Terry Nation, had planned to spin the pepperpots off into their own series, which would have also featured the Space Security Service from The Daleks' Master Plan. When the BBC decided against this, Nation pursued the project with the NBC network in America, but ultimately failed to secure a deal.
All this negotiating meant that Nation had little time to devote to writing for Doctor Who. As with The Power of the Daleks, Nation allowed former script editor David Whitaker to take on scripting duties.
Whitaker's initial pitch - simply called The Daleks – featured the Doctor and Edward Waterfield travelling back to Earth 20,000 BC to retrieve a caveman named Og, from whom the Doctor would deduce the essence of humanity. The Daleks' plan was to erase this quality from every generation of man, thereby eliminating Earth as a threat.
The Evil of the Daleks introduced Deborah Watling as new companion Victoria Waterfield. Watling was not the first choice to play the character, with actress Denise Buckley cast, then subsequently dropped. Debbie's father, Jack, would play Professor Travers in both Yeti stories the following season.
Famous faces to look out for are Windsor ("Lovely Boy") Davies from It Ain't Half Hot, Mum and Brigit Forsythe from Whatever Happened to the Likely Lads? Sonny Caldinez, who often played Ice Warriors in the series, featured as strong man Kemel.
All episodes except part 6 had individual episode titles: To Set a Trap (1), The Net Tightens (2), A Trial of Strength (3), A Test of Skill (4), The Human Factor (5) and The End of the Daleks (7). None of these were never seen on screen, however.
Most of the location filming for the story took place at Grim's Dyke Mansion House at Harrow Weald, Middlesex. Grim's Dyke had once been the home of Sir William Gilbert, of Gilbert and Sullivan fame. Hangars on Kendal Avenue in Ealing stood in for Gatwick Airport.
Director Derek Martinus was asked during the studio recording sessions by Head of Drama Sydney Newman to offer some hope that the Daleks weren't entirely destroyed – hence the inclusion of a shot of the Dalek Emperor clinging to life in its final scene.
The Evil of the Daleks is the only one to be repeated in the context of the series. The Wheel in Space concluded with the Doctor showing Zoe the whole adventure on the TARDIS view screen. Pity he didn't return it to the BBC archives afterwards...
Only episode two exists at the BBC, and will be released in November as part of the Lost in Time collection of orphan episodes from the Sixties. The soundtrack was released on CD, with linking narration from Frazer Hines, as part of the BBC Radio Collection in early August 2004. A short clip of two Daleks in the Emperor's chamber and some behind-the-scenes footage of the model work for episode seven also exist.