According to script editor Chris Boucher, the famous ending was meant as merely another season cliffhanger.
Janet Lees-Price, Paul Darrow's wife, accepted her guest role on the condition that her character be killed by Avon because she found the idea amusing.
Chris Boucher has claimed that the first news he received of the series being ended was the continuity announcement during the end credits.
The first proposal for the series' conclusion, titled Attack, involved Blake returning to lead an assault on the Federation on Earth, finally defeating them. This idea was rejected by Vere Lorrimer, who thought it "...would be like five men trying to defeat the German army". Influenced by the films Butch Cassidy and the Sundance Kid (1969) and The Wild Bunch (1969), Chris Boucher decided that concluding the series in a shoot-out would provide a more memorable ending. Apart from Blake, the characters' fates would be deliberately ambiguous in case a fifth series was commissioned.
Chris Boucher believed that the date on which the final episode was broadcast - 21 December 1981 - was unfortunate, and has since described himself as "the man who killed Father Christmas".