Downton Abbey star Jessica Brown Findlay has said Lady Sybil's world will be destroyed if she pursues her love for chauffeur Branson.
The headstrong character - who has shunned her life as a lady to become a nurse - may have turned down Branson's proposal, but still has feelings for him.
Jessica admitted: "They have such a wonderful connection.
"I think Branson is probably the first person that Sybil has ever been able to talk to about stuff that's been of interest and a meeting of similar minds and characters. But there is so much at risk for her with him. On paper it sounds so romantic, but there is so much more to lose."
She explained: "She might not appreciate or want to go down the path of being a lady, but she appreciates and respects her family. She doesn't hate them. She's not doing it out of bitterness and she loves them.
"So to do anything about it would mean so much more than some romantic gesture, it would mean the end of her world in that way. You'll have to keep watching."
Jessica stars alongside Felicity Jones in new film Albatross - released in cinemas on Friday October 14th - in which she plays rebellious teenager Emelia.
She said: "I was relieved to be out of the corset - it's definitely not the way to spend a comfortable day. That's what was so wonderful about Emelia, she can just slump around."
And she is about to begin work on the Downton Abbey Christmas special.
Jessica said: "We haven't started filming the upstairs section yet but I should imagine Christmas at Downton will be beautiful. I'm very much looking forward to seeing how it will look."