Naomi Watts wanted to play Princess Diana because she was such a "complex" woman.

The 44-year-old actress portrays the late royal in new movie Diana - which is based on the book Diana: Her Last Love and focuses on the last two years of her life including her romance with Dr. Hasnat Khan. Naomi initially turned down the part twice but was compelled to take on the role because she found Diana - the mother of British Princes William and Harry - so fascinating. Speaking at the world premiere of the film at the Odeon cinema in London's Leicester Square, she said, "Any woman I take on [on screen] I want them to be all things. I'm fascinated by women who are complex, full of contradictions, who are fun, intelligent but fragile at the same time. Someone who is going through something, some kind of transformation and this story is definitely that."

Naomi did a lot of research on Diana - the ex-wife of Prince Charles who tragically died in a Paris car crash in 1997 - and found her to be a very funny and mischievous person. The Hollywood star was determined to bring that side of the princess to the movie. "It seemed to me, in the research that I did, that Diana had a great spirit and a great sense of humour and a mischievous way and I definitely wanted to incorporate that in my portrayal," she added.

Naomi was joined on the red carpet by Naveen Andrews - who plays her on screen lover Dr. Khan - the film's director Oliver Hirschbiegel, Douglas Hodge, who portrays Diana's butler Paul Burrell, and star guests including Andy Serkis.