The Invasion of Time - Production

Production

The script is credited to David Agnew, a pseudonym often used by the BBC for work produced "in house" by contracted production team members. On this occasion it masks the authors Anthony Read (the series' script editor) and Graham Williams (series producer). This story was written as a replacement for another story, The Killers of the Dark by David Weir, which was considered too expensive and complex to shoot. The script was written in just two weeks, with four days for rewrites. Additionally, when asked about the unused script at a convention, Graham Williams, having forgotten the exact title, made up the name "Gin Sengh", as in The Killer Cats of Gin Sengh (or Geng Singh — the spelling being indeterminate), resulting in the fan myth that this was the original title. It was Robert Holmes who suggested to Graham Williams that this story be split into two segments, the first four episodes being based around the Vardans and the final two episodes being based around the Sontarans who come into the story at the end of episode 4.

Louise Jameson, who had already announced her departure from the show, reportedly wished for her character, Leela, to be killed at the end of the series, and was disappointed that Leela instead opted to stay behind on Gallifrey with Andred, even though nothing in the script suggests a romance between the two characters. The producers decided that killing off her character would be too traumatic for younger viewers.

An industrial strike, which was eventually resolved before production, forced the studio sets to be constructed within St Anne's Hospital as BBC's Christmas holiday specials were given priority in the regular studios. As a result of the industrial strike, Graham Williams was given the option of not producing the final six episodes of the season and have the money rollover into the next season. Williams rejected this because of the additional problem of inflation that year and didn't want the budgeted money to depreciate even further.

The Sontaran costumes were cumbersome and limited the field of vision of the actors wearing them, so much so that they are often seen tripping through and over props. At one point, a Sontaran (played by the actor Stuart Fell) nearly takes a fall after missing a short jump and landing on a pool chair. As the aliens originate on a planet of notably high gravity, however, their clumsiness is easily explained.

The closing credits of episodes three, four, and six feature the return of the section of Doctor Who theme commonly called the "Middle Eight", this sequence not having been heard since the early Jon Pertwee era.