Kristen Stewart has said she can't stop thinking about Princess Diana since she began preparing to play the late British royal in an upcoming movie.

The 31-year-old star will play Diana in a new movie Spencer, and said she sometimes falls asleep listening to her voice now.

"Getting to know Diana has been a really cool experience," she told OK! Magazine.

"She means a lot to me – but it’s all relatively new because I’m from LA and I didn’t grow up in England. Before this, she was not something that was at the forefront of my mind, because I lived so far away from it all.

"Now, I can’t stop thinking about her. I often wonder what she’d think about what’s going on in the world right now."

She added, "To be honest, I’ve now consumed pretty much all there is to consume in terms of videos and interviews. I’ve watched everything that you could hear or see. I even go to sleep with it on."

Emma Corrin recently portrayed Diana in The Crown and Stewart says the actress "killed it and she should be very proud of herself" and hailed her "moving" performance.