According to actress Wendy Richard, who played a supporting role: "It came from a brilliant book, but Cornel Wilde, God rest his soul, I don't think he did it justice when it came to the screenplay. He seemed to go over the top and get some bits of egg on his face."
Being Lynne Frederick's first film, it was also her first time away from home. Frederick's mother, Iris, personally asked her daughters older co-star, Wendy Richard, to look over fifteen year old Lynne. In her autobiography, Richard recalled that watching over Lynne was an arduous experience due to Lynne's "headstrong personality".
Lynne Frederick and Nigel Davenport reunited four years later in another science fiction film Phase IV (1974). Because Davenport had gotten along so well with Frederick in their first film together, he personally recommended Frederick for a role in Phase VI when a suitable female actress couldn't be found for the desired role.