Los Angeles, Oct 6 (IANS): Actress Kristen Stewart, who is all set to portray the late Princess of Wales Diana in upcoming drama 'Spencer', has opened up on the amount of research she did to get an understanding of her role.

Stewart told Entertainment Weekly: "There are contradictory materials from the horse's mouth. She doesn't always say the same thing in every interview, you know? There was a fickle nature, obviously, to a lot of the facts.

"She is, very sadly and very ironically, one of the most unknowable people in history, when all she wanted was to just be closer to people and bare herself."

Kristen said not everyone will think she's perfected her performance, but she's confident she's tackled the role in the right way, reports femalefirst.co.uk.

She added: "There was something just in absorbing her completely over the last six months leading up to this. I knew that I had hit some kind of elemental energy. If people have a lot to say about it not being a perfect impression, that's so okay with me."

The 'Twilight' star was just seven years old when Diana died in a car accident in 1997, she had no doubts about accepting the part.

She said: "I knew even before I read the script. I was like, 'You're not going to say no to this, because who would you be in that case?' I absolutely would have felt like such a coward. Especially given that I'm such an outsider. I'm not from the UK, I don't have any particular investment in the royal family.

"So I was kind of this really clean slate, and then could absorb her in a way that actually felt very instinctive, you know?"

The actress recently suggested the spirit of Diana gave her a "sign-off" for her performance.