Sheila Keith was primarily a comedy actress, but Pete Walker chose to cast her against type as the sadistic warden Walker (named after himself). This is because he feels that comedy actors make the best villains. Penny Irving likewise played against type - as she mostly appeared in sex comedies such as Carry on Dick and Are You Being Served.
The film was originally planned as a more stereotypical 'Girls Behind Bars' exploitation picture. However Pete Walker learned about a prison governess named Margaret Wakehurst in the Victorian period - who was dismissed from her position for treating her inmates too harshly. This helped form the story the film ended up taking.
The film was heavily criticized and damned by many who saw it as some kind of far-right moral finger wagging. This was mainly because of director Pete Walker's ironically subversive opening dedication "to those who are disturbed by today's lax moral codes and who eagerly await the return of corporal and capital punishment."
Penny Irving's character was nineteen years old. In reality Irving was over thirty at the time of filming.