Naomi Watts is fascinated by Princess Diana because her life was "filled with tragedy".
The 44-year-old actress portrays the late British royal - the ex-wife of Prince Charles and mother of Princes William and Harry who died in a Paris car crash in 1997 - in forthcoming biopic 'Diana' and she admits she was attracted to the role because of the "contradictions" in the princess' life.
She said: "I'm always interested in complicated women, in women who are full of contradictions; strength, vulnerability, success, loneliness and all those things.
"Diana exemplified that in major ways. She was a great mother, did a lot of things with AIDS charities and the landmines, and had an extraordinary life, but her life was also filled with tragedy and, of course, ended in the most tragic way."
Naomi - who has sons Sacha, five, and Samuel, four, with partner Liev Schreiber - initially turned down the part and was convinced she would "fail" in her portrayal of Diana because of the expectations the public will have and the love there is for the princess around the world.
She told Australia's Vogue magazine: "In the case of Diana, of course, there is a huge pressure to look right, to have good hair, to walk and speak like her.
"And I instantly thought, 'Oh no, I'm going to fail at that because the comparisons are going to be monumental.' "