The residents of 165 Eaton Place are in for a shock when Upstairs Downstairs returns to BBC1 next month, thanks to a lesbian romance involving new protagonists played by Emilia Fox and Alex Kingston.
Doctor Who star Kingston will join the cast as academic Dr Blanche Mottershead, the younger sister of matriarch Lady Holland. Her love interest will then arrive in the form of intellectual novelist Lady Portia Alresford, played by Fox.
Also among the newcomers for this new series is former Coronation Street star Sarah Lancashire, whose character Violet Whisset is set to become a love interest for butler Mr Pritchard (Adrian Scarborough).
Speaking at a screening of the first episode, writer Heidi Thomas, whose Sunday-night drama Call the Midwife is currently riding high in the ratings, said of Dr Blanche and Lady Portia's affair:
"I really don't want to give the game away because it lets you know things about the characters in the show ahead of time and I think it will spoil it for the audience.
"The pair certainly bring a whiff of scandal. They've been living abroad and now arrive in London. They try to be covert about their life. The series is set in 1938, where life was far less sexualised. When it gets exposed, though, they find a surprising ally."
Of comparisons to ITV1's heritage hit Downton Abbey - which also portrays the changing relationships between the wealthy and their servants - Ms Thomas added:
"Downton have had 18 hours of drama now and we are barely out of the starting blocks. I think this is a whole new chapter for us. We just don't reference Downton and I have only seen fragments of it myself."