The Australian Oscar-nominated actress stars in the title role of “Diana," a film about the last two years of Diana's life before she was killed in 1997 in a Paris car crash.

Watts, who was born in the UK but moved to Oz in her teens, told Total Film magazine: "I was very nervous about the accent.

"She had a very distinct voice - she came from aristocracy so she was quite posh, but there was a warmth there, too. Her accent wasn't too 'fruity'.

"She also had this thing where the bottom half of her face didn't move that much."

The “Impossible” star, who has previously admitted she is dreading the public reaction to her performance, recreates Diana's famous Panorama interview in the film, and revealed she listened to it constantly.

The feature film about Princess Diana's torrid love affair with a heart surgeon will have its world premiere in London just days after the sixteenth anniversary of her death.

It opens September 5 in the UK and October 10 in Australian cinemas.

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