Naomi Watts wedged cocktail stick in her mouth to perfect Diana look

Actress Naomi Watts walked around with a cocktail stick wedged in her mouth as she prepared to play Princess Diana in a new biopic in an effort to take on the tragic royal's facial features.

The Mulholland Drive star decided to alter the physical structure of her face for the role and went to great lengths to become more like Diana.

She tells Empire magazine, "I didn't just want to appear like her, it's also about the tone of her voice and the way she moved her face. It's completely opposite of how I move my face. I move my face on the right-hand side and she moves hers to the left.

"I had to walk around with a cocktail stick in my mouth to paralyze the right-hand side of my face for weeks."

She also spent weeks trying to perfect Diana's accent, confessing she was "very nervous" about authentically playing the dead royal.

She tells Total Film, "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."

Watts' film Diana is released later this year (13).