The episode was primarily written by Russell T Davies after Minogue was cast. Davies described his pitch to Minogue as "busking". The character of Astrid Peth was written for Minogue. Davies later stated that Minogue was a "very exceptional case"; he considered writing a role specifically for one actor "dangerous territory" because the desired actor may be unavailable or decline the part. In early drafts of the episode, Astrid did not die. Davies decided Astrid's death was necessary to allow Minogue focus on her musical career. Davies described the original nature of her death—falling over a precipice during a fight with Capricorn—as "fleeting". He intensified the scene by changing Max from mobile to cybernetic and Astrid's attack from an altercation to a fork-lift truck. Davies felt the revised scene was "such a beautiful image" and romanticised Astrid's "ultimate sacrifice".