 The screenplay to this film was credited to producer  Milton Subotsky (qv), with additional material by  David Whitaker (II) (qv). In fact, Dalek creator  Terry Nation (qv) only agreed to license his teleplay to Subotsky  if Whitaker (who was Nations script editor when he wrote the  original teleplay) was hired to adapt it. A deal was therefore  struck that would allow Subotsky to receive the credit despite the  screenplay actually being written by Whitaker.