Are you enjoying being such a rebel?
‘I’m loving it, it’s very freeing. Everything's allowed.’
Rose is quite a liability.
‘Yeah, very unaware of the consequences of her actions, and no ability to abide by rules.’
She's at the centre of the bright young things as the 1920s – how was that to film?
‘Really exciting. The world of the flapper, live free, wild and young – that energy is intoxicating. It’s nice to inject that into the more controlled Downton way of living. And there's loads of dancing. It’s really funny doing it all together, treading on each other’s toes. You don’t expect to see Jim [Carter, who plays Carson] doing the one-step. But he’s very good!’
Does Rose have love interests this year?
‘There’s all sorts of potential for that this year.’ Who does Rose bond with most in the family? ‘Cora, I think. She doesn’t have any real love in her life, so she’s searching for that.’
Do you like Rose?
‘I have a love-hate relationship with her. She’s really shallow, but she’s got a big heart – she’s so young, but her depth of emotional perspective gets bigger this year.’
Do you use Twitter?
‘I have an account but I don’t use it. It’s dangerous – if you search yourself then read things you don’t want to, it’s tough. It’s a temptation, so I’m not using Twitter for the time being.’
There’s a huge celebrity fanbase for ‘Downton’. Has anyone surprised you?
‘We talk about it as a cast. Apparently Mick Jagger loves it. And my brothers aren’t famous, but they love it. They started watching because of me, but now they’re hooked. ‘
Are you happy to stay as long as you can?
‘I’m having such a great time – I’ll be in it as long as they'll have me.’