The nude extras in the group shower scene were from a local hippie commune.
Olivia Hussey almost accidentally cut off Roger Ward's hands in one scene. When the director yelled cut, she took the order the wrong way during the scene and Ward just pulled his hands out of the way in the nick of time.
The role required some brief nudity for Olivia Hussey in a shower scene where her breasts would be fully exposed. Hussey humbly requested that she not be required to do the nudity, and per her request, a body double was hired. The topless shot with the body double appeared on screen for approximately two seconds. When Hussey was on screen, she had her breasts covered with her arms and her long waist-length hair. In her 2018 memoir, Hussey confessed "Ironically, when I saw the film, and saw what the body double looked like, I wished I'd done the damned nudity. I had a much better body than she did."
Actor Michael Craig's head-of-prison-camp character Charles Thatcher was named after British Prime Minister Margaret Thatcher who was in office at the time the film was made and released. The UK video release retitled the film 'Blood Camp Thatcher'.
Despite flopping critically and financially in the US and Australia, when it was finally released in the UK (amidst a major blizzard) the film broke box office records, recovering much of any losses made.