Naomi Watts says Princess Diana gave her ''permission'' to play her.

The 44-year-old actress takes on the title role in new biopic 'Diana' and has insisted while playing the British royal she felt her ''presence''.

She told the Mail on Sunday newspaper's Event magazine: ''There were definitely moments when I felt Diana's presence - I dreamed about her a lot, too, and that's a first. I kept wondering to myself: 'Would she have liked it?'

''So I found myself constantly asking for her permission to carry on. I had saturated myself with Diana and her life and I felt this enormous responsibility of playing this iconic woman.

''It felt like I was spending a lot of time with her. There was one particularly moment when I felt her permission was granted. That won't sound right in print, I know.''

'The Impossible' star admitted accepting the role wasn't an easy decision and she found the prospect of it ''very daunting''.

She added: ''There was a lot of hesitation on my part before I agreed to do it. Obviously I was taking on one of the most famous women of my time and an awful lot of pressure comes with that.

''You want to get it right, and everybody is going to have an opinion on the film and how she should be portrayed. It's very daunting.

''But then I also knew that the exciting roles, the best roles, come with a risk. In the end I decided that I couldn't not do it ... But it was definitely the hardest thing I've ever done. It's as close as I ever want to get to a character.''