- Missing Episode: Only 20 of the show's 49 episodes survive:
- Season One is the best represented in the archive, with 10 of its 12 episodes surviving.
- Season Two fared less well, with only four of its 13 episodes still existing.
- Season Three, the first to be filmed in colour, has only one of its 13 episodes surviving. Unlike many BBC colour programmes of the era, it still exists on its original colour master tape.
- Season Four fared better than the previous two, with 5 of 13 episodes surviving.
Trivia / Out Of The Unknown