Naomi Watts had to paralyse the right-side of her face to play Princess Diana.

The 44-year-old actress plays the late Princess of Wales in new biopic 'Diana' and she was so determined to perfect her mannerisms that she was forced to wander around with a wooden cylindrical stick in her chops in order to change the way her mouth moved.

Speaking to Empire magazine, she said: ''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 the opposite of how I move my face. I move my face on the right-hand side and she moved her son the left.

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

The blonde beauty admits she toyed with the idea of playing the British royal for a while because she was concerned about how people would take to her and whether they would criticise her for the way she portrayed the role.

She explained: ''A lot more pressure and a lot more fear that comes with that pressure. I wrestled with the decision of actually doing it because of that. I was afraid of all the comparisons that people would make: not the right nose, not tall enough, not the right voice.''