Naomi Watts became so fixated on Princess Diana's interview with Martin Bashir she even watched it while working out.
The actress plays the late Princess of Wales in new biopic 'Diana' and was so determined to perfect her mannerisms she repeatedly watched footage of her explosive interview, originally broadcast in 1995.
Naomi told Hello! magazine: "I ran the Martin Bashir TV interview so often that it got to the point where I was watching it on my iPhone while I was out jogging
"I had five minutes of her walk, five minutes of her wave, five minutes of her laugh that I'd watch again and again.
"She laughed a lot, actually, and had a cheeky sense of humour and would crack jokes you wouldn't expect a princess to crack."
The movie focuses on the last two years of Diana's life where - following her divorce from Prince Charles - she had a relationship with heart surgeon Hasnat Khan, before her tragic death in a car crash in 1997.
Speaking of Diana's relationship with the doctor, Naomi added: "He was someone she trusted right away. She was fascinated by his mind.
"He was clever and traditional. She knew he was never going to exploit her. People would always be following her: but she did end up finding a connection with this one man."
However, Doctor Khan himself is not happy with the way he thinks he will be portrayed in the film, and said seeing even a single still from the movie has put him off ever watching it.
He said: "I don't see this movie doing well at all. It is based on gossip and Diana's friends talking about a relationship that they didn't know much about, and some of my relatives who didn't know much about it either.
"You could tell from that picture it is all just presumed about how we would behave with each other, and they have got it completely wrong."
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