Diana, a biopic of the late princess of Wales who died in a Paris car crash, has its world premiere on Thursday with its star Naomi Watts already defending her involvement in the controversial film.
The movie follows Diana's romance with London-based Pakistani surgeon Hasnat Khan, whom many friends of the princess say was her real love and the man she allegedly called "Mr Wonderful".
Based on Kate Snell's 2001 book Diana: Her Last Love, the film suggests that Diana started dating Dodi Fayed to make Khan jealous - a claim challenged by many close to the princess.
Diana and Fayed died when the Mercedes in which they were travelling slammed into a pillar in a Paris road tunnel in 1997 while being pursued by press photographers.
Diana and heir to the British throne Prince Charles divorced in 1996 after 15 turbulent years of marriage which produced two sons, Princes William and Harry.
Watts, dressed in a figure-hugging white gown, was joined on the red carpet at London's Leicester Square by British-Indian actor Naveen Andrews, who plays her on-screen lover.
The British-Australian actress who came to prominence in Mulholland Drive in 2001, admitted that she was taking a risk by accepting the role of the "People's Princess".
She was asked if she felt the film would offend Diana's sons, reports The Straits Times. "Hopefully if they get to see the film, they will feel that we have done it in a respectful and sensitive way," she told BBC TV.
"We try to honour the depiction of her character in the best possible way." But on Wednesday, Watts stormed out of a separate interview with BBC radio, apparently because a question offended her.
The surprised presenter, Simon Mayo, tweeted that Watts had "seemed a tad uncomfortable with the questions." The film has been largely ignored by the royal family.
Its producer Robert Bernstein claims the royals gave some help in allowing filming in Kensington Gardens, where Diana used to go jogging, although a spokesman for the royals told AFP the area was not under its jurisdiction.