Bradley is sometimes seen at the start of an episode making some rubbish film, only to be called by his handler “Mr Parminter” played by Barry Morse (Space: 1999) to go on a mission. So Bradley skips the movie set (and no-one minds) and does his investigations.
To help him is Vince Elliot, played by Stuart Damon (The Champions) and Diane Marsh played by Catherine Schell (Space: 1999).
Except, it wasn’t like that. Damon appears briefly and uncredited in the first couple of episodes, but then disappears. He was kept under contract and paid, but never again appeared in the series. Why? Because he was considerably taller than Gene Barry, who claimed 6′ but was clearly shorter, and Barry didn’t like it.
So actor Garrick Hagon was brought in to play Gavin Taylor, but he only makes a few appearances.
In fact, Catherine Schell also rarely appears. Again, Barry had her removed because of her height. The only episodes where she really does anything are ones when Barry is not appearing (he went off on holiday), then she and “Mr Parminter” get real things to do and the series improves dramatically.
Other random and unspecified people appear to help at times, but it gets hard to follow who they are and what they are doing.
Also in the mix was Bradley’s butler Brandon, played by Dennis Price in a slightly approximate and pointless way. But only a few episodes at the end.