In the fourth season, Leslie Grantham played the murderer Colonel Mustard. In real life, Grantham was a convicted murderer. He murdered the West German taxi driver Felix Reese in Osnabrück, Lower Saxony on December 3, 1966. He was convicted of murder in 1967 and sentenced to life imprisonment but only served ten years.
Based on the classic board game of the same name by Waddingtons.
The series premiered 5 years after the release of the big screen adaptation of the board game Clue (1985).
Susan George, who played Mrs. Peacock in the third series, injured her ankle when she fell down the stairs in the main hall.
Stephanie Beacham, who played Mrs. Peacock in the first series, revealed that she and Tracy-Louise Ward had to have several articles of clothing draped over them while in between scenes to protect them from the extremely cold mansion. Beacham said that in almost every scene she has at least three thermal vests under her costumes.