The Help star Jessica Chastain is slated to play Princess Diana in a new Hollywood movie about the royal's love affair with heart surgeon Dr Hasnat Khan.

The 30-year-old actress has already signed up to appear in the film, according to a report from Anne Thompson on Hollywood.

The movie, titled Caught In Flight, examines Diana's secretive relationship with Dr Kahn.

The couple began dating in 1995 and went to great efforts to keep their two-year affair away from the public eye. They split in 1997, but many commentators see Dr Kahn as Diana's one great love - a man she dubbed "Mr Wonderful" and was rumoured to have considered converting to Islam for, in order to marry him.

The medic has spoken only once about his former partner since her death in 1997. "I found her a very normal person with great qualities," he said, in the 2008 interview. "I think she did great work all over the world not just for the UK but for everyone. That is very important."

German film-maker Oliver Hirschbiegel is set to direct the film. He is the man behind 2004 critically acclaimed biopic Downfall, which chartered the last days of Adolf Hitler's regime.

Filming will begin next year in Paris, with set locations also extending to Pakistan, Angola and the South of France.

Jessica has seen her Hollywood profile blossom this year, with roles in The Tree Of Life opposite Brad Pitt and The Help, the movie adaptation of Kathryn Stockett's hit novel. She will next appear in apocalyptic drama Take Shelter and Horizons, with Tom Cruise.

Jessica Chastain tipped to play Diana