Ian Hendry, who guest stars as Irwin Gunner (The Flyer) starred with Patrick Macnee in the first season of parent series The Avengers (1961), where he actually had top billing over Macnee in his rôle of Dr David Keel. The vast majority of this opening run is sadly missing from TV archives and thought to be probably lost forever - only the first 15 minutes of the very first episode, Hot Snow (1961), and three complete later episodes, Girl on the Trapeze (1961), (which is one of only two editions not to feature the character of Steed), The Frighteners (1961) and Tunnel of Fear (1961) are known to have been recovered and preserved.
A keen athlete in his younger years, Hendry had genuinely had experience of trapeze work.
The villain Cledge is played by Barry Jackson, who had a recurring role in Midsomer Murders as the forensic specialist Dr. Bullard.
The BBFC for video release of the series gave 4 of the first 7 a 12 rating. While the remaining 22 have a PG rating.