Kristen Stewart on tackling the 'scary and ambitious' role of Princess Diana

Click the play button above to listen to Kristen Stewart's full conversation with Tom Power.

Kristen Stewart has been lauded by critics for her haunting portrayal of the late Princess Diana in director Pablo Larraín's upcoming historical drama, Spencer, but she wasn't confident she could pull it off at first.

Before even reading the script, Stewart said she "irresponsibly" agreed to take on the role, despite feeling unsure if she could play someone as iconic, celebrated and complex as the former Princess of Wales. At this stage in her career, however, she said she's compelled to say yes to projects that seem impossible.

"Having really not had an enormous interaction or relationship to the Royal Family as an entity — or Diana as anything more than a really sparkly figure that … is very, sort of, attractive — I said yes, because I thought it was scary and ambitious," she told Q's Tom Power in an interview.

WATCH | Official teaser trailer for Spencer:

Set in December 1991, Spencer imagines a precarious Christmas holiday with the Royal Family as Princess Diana reaches a tumultuous turning point in her marriage to Prince Charles. The film sees her reclaiming her own last name, Spencer, before setting out on her tragically short-lived path to independence.

The first footage from the film released to the public was a roughly one-minute teaser trailer, which reveals only two words from Stewart, but that was enough to get audiences talking about the actor's impressive accent.

Stewart laughed as she recalled watching the teaser for the first time. "I think the trailer is great. I just was like, 'Oh, come on, give them like one more line!'"

More than just nailing the accent, Stewart knew emulating Princess Diana's unique way of "being and moving through the world" would also present her with a challenge.

"I just feel like when you watch interviews with her, or you see her walk out of a building and into a car, you just, like, never know what's going to happen," she said. "And that's something that, you know, that she was just born with…. In talking about it, you realize it's like, 'Well, can I play this incredible, amazing, attractive, like, beautiful, empathetic Mother Teresa figure?' I don't know."

The one thing that felt sure, the one thing that she knew, was how to be a mom.- Kristen Stewart

Luckily, Stewart had innumerable perspectives to draw on while completing her research for the role, which included several memoirs. She said she did her best to absorb what she could from those sources, but chose not to focus on specific traits when it came time to shoot to keep the portrayal from feeling like a "bad impersonation."

"I never felt like, 'Oh, we need to make sure that we get this detail in there.' I just felt like the right ones would seep in and then not feel overt."

There was only one aspect of Princess Diana (beyond her voice and physicality) that Stewart knew she wanted to preserve as accurately as possible in her performance.

"The one thing that I get very clearly, clearly from her is her — was her — ability to keep the little bubble around her and her boys," said Stewart. "The one thing that felt sure, the one thing that she knew, was how to be a mom…. And that was, again, daunting. I'm not a mom yet. But I just felt that so strongly. I thought that we would not have done our jobs even close to correct unless we got that."

WATCH | Kristen Stewart's full interview with Tom Power:

On relating to Princess Diana

Being a Hollywood celebrity is very different from being a member of the Royal Family, but Stewart said in certain ways she can relate to Princess Diana.

The actor commented on the "weird dichotomy" of being a public figure — both known and unknown at the same time — comparing it to how Princess Diana's desire to connect with people was at odds with her need to escape public life.

"I can relate to that [feeling]," said Stewart. "Like, I want to control how people see me, but then, also, I want to get naked in public and do movies where I completely reveal myself totally. But then, you know, not all the time…. You just want a little bit of agency and control over that."

When it comes to the work she's currently drawn to, Stewart cited films that feel "incredibly internal," adding that Spencer is the perfect example of this, as it allows the audience to imagine what Princess Diana may have felt at the time her marriage was falling apart.

"I think we're in this beautiful kind of period [in film] where, you know, women are allowed to really find [their] voice and be weird and honest about what it feels like to be alive with a female body," said Stewart. "And I don't think that we've remotely even scratched the surface of, yeah, what that feels like, what it looks like, what it smells like, what it tastes like."

Written by Vivian Rashotte. Produced by Vanessa Nigro.