The Asphyx

The main credits state that the film's soundtrack was recorded using a 4-channel quadraphonic sound system. Sadly, there appears to be no evidence of it ever being exhibited in this manner.

Toward the end of the film Robert Powell picks up a glass beaker. It has the Pyrex stamp on it and its volume is stated as 600ml. Victorian England used imperial (non-metric) measures, and Pyrex was not invented until 1915.

The film was originally shot in Todd-AO 35, a wide-screen process which is normally viewed at 2.35:1. The 1995 UK video featured a much shorter print and missed around 12 minutes of footage including dialogue scenes, an anti-hanging protest before the execution, and the removal of a scene showing the now-immortalized guinea pig being released from its cage. The 2004 Anchor Bay UK DVD features the same print and is presented in an anamorphic 1.85:1 ratio and also uses a pan & scan technique, thus cropping much of the print into a false version of wide-screen. The 2010 Odeon DVD features both the shorter and longer original prints in genuine widescreen.