London, Oct 12 (IANS): Actress Kristen Stewart, who portrays Princess Diana in the new biographical drama film 'Spencer', says it was a nerve-wracking experience, and the anxiousness led her to develop a pain in her jaw.

Stewart told BBC News: "I had TMJ (her jaw stayed shut) to the point where I was like, completely locked up. I was like, 'Huh, I guess I'm really nervous' - I was really tripping out until we started."

She shared that she didn't actually know a huge amount about the Royal Family before she accepted the role, reports femalefirst.co.uk.

Stewart said: "I didn't have the most developed or defined relationship with the Royal Family in generally. I didn't grow up following the sort of saga. Obviously I do live on planet earth, and her impact was so immense and emotional, even for somebody who was seven when she passed away."

Stewart did a lot of research before she started shooting the new movie.

The actress even took to watching 'The Crown' as part of her preparations for the role.

She said: "I read everything, I wanted every photo ... watched all the interviews that I could get my hands on.

"I watched 'The Crown', I watched every iteration of interpretation. I just tried to absorb her in an emotional and general way, and then trust the process, and expect her to show up."

She also felt a need to "protect" the late Princess.

The actress added: "I had to just not focus on other people's idea of her, and really focus on my own. And that in itself was just so distinct and specific to me."