This was the first ever movie to receive a rating from the MPAA in 1968.
This was Hammer Films' most profitable movie.
Hammer stalwart Terence Fisher was due to direct this until he was forced to bow out following an automobile accident, leaving cameraman Freddie Francis at the helm.
According to the inscription on the marker ("Gisela Heinz 1885 - 1905") of the just-stolen coffin, the date of the action in this film is within a year or so of 1905.
During production, Hammer Productions became the first movie studio to be presented with the Queen's Award for Industry.