The colour master videotape was wiped by the BBC in the 1970s and although colour versions were sold overseas, only 16mm black-and-white film prints were retained by BBC enterprises. Some short poor quality colour clips existed from this episode thanks to a domestic recording made in the United States. However, this episode was restored to colour for the DVD release in 2013 using the chroma dots discovered in the film prints.
This episode was watched by 7.3 million viewers on its original transmission.
Barnham was originally killed much earlier in the story.