In the ending scene of episode 21 "A Death in the Family", Danny Wilde (Tony Curtis), Brett Sinclair (Roger Moore) and the Duke of Caith (Roland Culver)are preparing to go out each with a lady companion. The lady supposed to accompany The Duke of Caith is introduced by Brett Sinclair as "Mrs. Schwartz" and actually played by a disguised Tony Curtis. Tony Curtis' real name is Bernard Schwartz.
The opening scene, where uncle Rudolph, played by Roger Moore, is killed by a model tank, was taken on the premises of Moore's manor. Roger Moore lived at Sherwood House for eight years between 1970 and 1978, during which time he shot Live And Let Die, The Man With The Golden Gun and The Spy Who Loved Me. The property was built in 1920 and lies 20 miles west of central London in the village of Denham, Buckinghamshire.
Terry Nation's script lifts significantly from Roy Horniman's novel "Israel Rank", filmed in 1949 as "Kind Hearts and Coronets". This is echoed in Roger Moore playing several roles, just as Alec Guinness did in the movie.
This episode was recently omitted from the transmission of the whole series here in the UK, presumably due to the death of Elizabeth II.
On french version, Randolph is sometimes described as Brett's dad.