When Jean Marsh and Eileen Atkins came up with the original idea for Upstairs Downstairs, they envisaged it as a comedy called Behind the Green Baize Door.
David Langton (Richard Bellamy), Gordon Jackson (Hudson), Angela Baddeley (Mrs Bridges) and Jean Marsh (Rose Buck) are the only actors to appear in both the first and last episodes of the series.
By season 3, 165 Eaton Place consisted of: 6 bedrooms, 2 bathrooms, dressing room, dining room, drawing room, morning room, library, study, and another room which changed from gaming room to whatever the family needed.