In the original script, Lexa had simply vanished from the action once she had served her purpose within the narrative. Christopher H. Bidmead suggested her act of self-sacrifice as a more dramatic end for the character.
Mysteriously, the end-titles theme music is played a whole-step lower than normal (curiously, this puts the tune back in its original key of E minor).
This episode runs for just over 19 minutes making it one of the shortest ever episodes of Doctor Who to be broadcast. At least three minutes of that are titles, and recap and credits.
This episode was watched by 4.7 million viewers on its original transmission.
Final acting role of Edward Underdown.