Naomi Watts will play Princess Diana in a major biopic of her last years, reports the BBC. The 43-year-old Watts landed the plum role in Caught in Flight, which is scheduled to start filming this year, notes AP. It is expected to focus on her relationship with heart surgeon Hasnat Khan, which lasted from 1995 until a few months before she died in August 1997. Filmmakers say it will explore how Diana found "true personal happiness for the first time." The movie by Britain's Ecosse Films will be directed by Oliver Hirschbiegel, best known for his Hitler film Downfall. (More Naomi Watts stories.)