Writer Troy Kennedy Martin was greatly influenced by the political climate of the time, dominated by the Thatcher government, and the aura of secrecy surrounding the nuclear industry – and by the implications of the Gaia hypothesis of environmentalist James Lovelock; these combined to his crafting a thriller that mingled real world concerns with mythic and mystical elements. Kennedy Martin's original ending was more fantastic than that eventually used in the finished serial: he had proposed that Craven would turn into a tree but this was vetoed by members of the cast and crew.