Aged just 22, Brown-Findlay is also carrying a movie for the first time; in Albatross she plays Emelia, a sassy working-class girl who comes to work in a hotel owned by Jonathan (Sebastian Koch), a published author with writer's block. She befriends his impressionable daughter Beth (played by Felicity Jones), but this friendship doesn't prevent her from having an affair with Jonathan. The part proves she can play a completely different type of character. And in an age when actors are often cast based on their perceived public persona, it's a smart move to offer two polar opposites as your first roles.
This begs the question whether Jessica is more like Emelia or Lady Sybil: "Umm, I don't know," comes the unrevealing response. "I think maybe Emelia is me under a microscope, under a microscope, under a microscope and times a million. I remember stealing some pick'n'mix when I was seven; when I got out of the shop, I burst into tears. Emelia wouldn't think twice about it. She is someone who is very flamboyant and then underneath has a lot going on. I think that is a far more realistic person and that is quite like me."
As for Lady Sybil, who is now proving that action on women's rights speaks louder than words: "Sybil is so good and so righteous and has such a great moral centre. I don't know if I'm so righteous."
As a young girl, Brown-Findlay's passion was ballet. She turned to acting when injury ruled out a career pirouetting. As such, most of her experience of acting has been learnt on the job; much of Downton has been spent observing Maggie Smith et al at work - and learning that it's okay to make mistakes.
One thing that she struggles with is playing angry. "Sometimes when a scene is written or directed to be shouted or played incredibly angrily, I always think it's way more terrifying when someone is fuming and talks in a very calm way. I always want people to shout at me if they're angry - it freaks me out that whole thing of, 'I'm not angry I'm just disappointed'."
I jokingly wonder if that's how she treats her boyfriend, Thomas Campbell, whom she met while studying fine art at Central Saint Martins College of Art. "Poor bloke," comes the equally tongue-in-cheek reply.
To get into the mindset of playing a 17-year-old for Albatross, Brown-Findlay made playlists of music that she listened to when she was 17. "Everything you listen to when you are 17 should be embarrassing, otherwise you are way too cool," she wisely points out. Limp Bizkit and their like have been replaced by Bruce Springsteen, Joy Division and Metronomy; "You have to download their second album, it's insane," she counsels.
Her fingers are adorned with rings; several of them stacked one atop another on one digit. When I comment on them, it leads her to say, "I just really think every job I do, I get this gypsy attitude to money. If I invest in gold it's never going to lose value and if I keep it all on me, if I ever find myself estranged, I can get myself home by pawning it off."
One of the rings, she says, she went halves on with her mother for her 21st birthday present. Her mother, a teacher's assistant, declared it too expensive at first. Her father is a financial advisor and the family home is in the well-to-do village of Cookham, Berkshire. "I think they are a little bit baffled," she says of her folks. "I think they've always thought I was just a bit weird - I used to dress in old clothes and listen to old-fashioned music - but that's fine. My nan and grandad live really nearby and my grandad is a carpenter by trade. He's amazing and my nan is my best friend ever. It's cool. When I was younger it felt like I had two sets of parents."
She admits that she's forever getting told off for being superstitious. "I do so many things. Like when I was younger, if I drove past a house that I didn't want to live in, I'd hold my breath. Driving around somewhere like Slough I'd go blue in the face. Drains! Walking down Old Compton St in London I don't even have to look down anymore, I just jump occasionally. If you see a big weirdo jumping, that's me.
"Before I go on stage, I knock three times. Three is my lucky number; I once went into an audition and was number 333 and got the best part ever."
That was back in her dancing days. But for now Brown-Findlay doesn't need to rely on chance; it's her talent, looks and weight of personality that have everyone talking.
Lowdown
Who: Jessica Brown-Findlay who plays Lady Sybil in Downton Abbey
When and where: Downton Abbey's second series starts Tuesday October 18 on Prime
- TimeOut / The Independent