He may also have directed, without on-screen credit, the third episode of the Doctor Who story The Reign of Terror, "A Change of Identity" when Henric Hirsch was taken ill and collapsed during recording.
However, Gorrie claimed in later years to have no memory of working on The Reign of Terror, so it is possible that the director of "A Change of Identity" may actually have been someone else, whose identity remains unknown to this day.
During recording of the first episode of The Keys of Marinus, "The Sea of Death", it had to be pointed out to Gorrie by Raymond Cusick that although described in the script, the scene where a Voord falls through a secret panel in the wall of the Conscience Machine building and plunges down a shaft straight into a pool of acid needed to be explained for the viewers, i.e. by their either hearing a scream and a splash or seeing something happen. Originally, Gorrie had intended to have the Voord simply falling through the panel and that would have been it; Cusick explained that this planned shot wouldn't work as the viewers would merely assume the Voord had fallen into a broom cupboard.
- Internet Movie Database at the