Following the successful realisation of the Doctor's home planet of Gallifrey on screen in "The Deadly Assassin", producer Graham Williams wanted another Gallifrey story. Script editor Anthony Read approached David Weir with whom he had worked before. Weir's script, a six-part story, was planned as the final story of Season 15 and was commissioned on 18 July 1977. Weir's script had elements drawn from Asian cultures, and included a race of cat-people with links to Gallifrey. Scenes included a gladiatorial duel in a stadium filled with cat-people. Read and director Gerald Blake, upon reading the finished script, determined that the story would be impossible to shoot on "Doctor Who"'s budget and the story was abandoned mid-August 1977. With only two weeks to spare before filming, Read and Williams quickly co-wrote a replacement script in the form of "The Invasion of Time". When asked about Weir's story at a fan convention years later, Williams could not recall its title and made up the name "The Killer Cats of Geng Singh", by which title the story became widely known in fan circles.