According to various books on Hammer films, this film went over schedule and some key scenes were never filmed. Ironically Rank called it Hammer's best film in a decade.

Shot in six weeks.

Robert Tayman was dubbed by David de Keyser.

Laurence Payne was an 11th hour casting choice replacing Anton Rodgers who dropped out because of illness.

Serena and Milovan Vesnitch both receive "introducing" credits.