Lily James's 'inner battle' on social media

"I am a hypocrite," laughs Lily James.

It's not something you'd normally hear one of the UK's top actresses admit to - but the reason for Daisy Ridley's recent decision to leave social media has caused Lily to reflect.

Star Wars actress Daisy deleted her accounts last year because she said social media was bad for people's mental health.

"I completely and utterly relate to that," says Lily, speaking to BBC News ahead of the release of her latest film, Darkest Hour.

"I believe it to be true, and therefore I am a hypocrite. I am on [social media], and I have a constant inner battle about it.

"I'm not on Twitter, I don't want to always have something to say, I want to save that for my life.

"Also I think, especially as a young person, you change your opinions every second, so [you shouldn't] put something down in concrete that's going to come back and haunt you."

That certainly explains her absence from Twitter - but there's no doubt Lily's Instagram game is strong.

"Instagram you can use for all sorts of different reasons and that can be powerful. But I do worry about obsession and about perfection and about always presenting your life in a certain way, which is very untrue to how you go about your day.

"We go through all sorts of different emotions and Instagram makes it look like everything's perfect, and that's rubbish."

Lily plays Winston Churchill's secretary Elizabeth Leyton in Darkest Hour, which is released in UK cinemas this weekend.

On Tuesday, it was nominated for nine awards at this year's Baftas - including best actor for Gary Oldman, who stars as Winston Churchill. He won the same accolade at this year's Golden Globes.

Darkest Hour is Lily's first major film appearance since Baby Driver last summer, in which she co-starred with Kevin Spacey, although they had few scenes together.

Lily plays Churchill's secretary Elizabeth Layton

Given the string of allegations which have recently emerged against the former House of Cards star, and other major Hollywood figures, is she glad the issue is being talked about in Hollywood?

"Yes, completely. I think the bravery of everyone that's come forward and spoken, the fact that they've shared their pain and their stories in order to make change is the most admirable brilliant thing.

"And I'm so hopeful that now there's going to be a huge shift in how that power balance has been and how people have been treated."

The actress adds that she agrees with Meryl Streep's recent comments that there may have been less abuse in the entertainment industry had there been more women in positions of power.

"There'd be less room for it," Lily says. "I'm lucky enough to have just made a film [Little Woods, released later this year] with a young female director, the producers were women and the story was about women, and it was such a change. I hadn't experienced that before.

"That needs to become the norm, commonplace, I want to work with female directors as much as I do male directors, I want to look around the crew and not be surrounded by men, so that will be something that hopefully is changing, and I'm so inspired by all these people that are making their voices heard."

Darkest Hour focuses on Churchill's first month in power - in which he struggles with whether or not to attempt to negotiate a peace deal with Nazi Germany.

The World War II drama probably isn't the sort of film Lily's young fans would normally have much interest in, certainly not to the same degree as many of her previous movies like Cinderella.

But the 28-year-old thinks it's important the film reaches a young audience, "for all sorts of reasons".

"We can learn so much from our history," she says.

"Especially at the moment. When you watch a film about a very powerful leader at the time where he really was the voice and will of the people and united the country.

"I don't think there's necessarily that kind of strength in leaders at the moment, so I think it's quite inspiring."

Gary Oldman plays Winston Churchill in Darkest Hour

Lily's next role is ever-so-slightly different to Darkest Hour - Mamma Mia 2: Here We Go Again, which is released in the summer.

"All I can really say is I had one of the greatest experiences of my life," Lily says of filming the sequel to the hugely successful Abba musical.

• Read more: 6 shocks from the Mamma Mia 2 trailer

"To work on both Mamma Mia and Darkest Hour, given how different they are... with Mamma Mia all the old cast are back, so I'm working with actors who are Oscar winners, it's sort of mind-blowing and I'm very excited and grateful about that.

"The music is wonderful, there are new songs which are going to be huge hits, and there are old songs which are back again," she adds.

Asked for her favourite song by the Swedish quartet, she laughs: "Ohh, that's a tough one - The Name of the Game, Chiquitita, Super Trouper... I'm a big Abba fan as you might be able to tell."

Darkest Hour is released in the UK on 11 January.