From WENN.com

The star was cast in the film, which tells the story of the last two years in the life of Charles, Prince of Wales' former wife, who died in a car crash in Paris, France in 1997.

Watts has had her long locks trimmed into Diana's trademark wavy bob, and in photos taken on the movie set she can be seen bearing an uncanny resemblance to the British royal by adopting her famous doe-eyed facial expression.

The movie is due for release next year (13).