Charlize Theron for Diana movie?

Charlize Theron could play Britain's Princess Diana in a movie adaptation of Ken Wharfe's book 'Diana: Closely Guarded Secret'.

Charlize Theron could be set to play Britain's Princess Diana in a Hollywood movie.

The South African-born actress is up against British star Keira Knightley for the role, which tells the tale of the princess' relationship with former bodyguard Ken Wharfe, who is to be played by Ewan McGregor.

The movie will be produced by BAFTA award-winning Stephen Evans, who wants to make a film based on Wharfe's controversial book 'Diana: Closely Guarded Secret', detailing the eight years he spent with the princess - who died in 1997 - as her personal protection officer.

Studio Pathe is hoping for a 2011 release to mark what would have been the princess' 50th birthday.

An insider told the Daily Mail: "There's a buzz about this. Pathe also made 'The Duchess', which starred Keira as Georgiana, the fifth Duchess of Devonshire - the great-great-great-great aunt of Diana - and controversially used an image of Diana to trail the movie.

"They believe the footage made the film a big hit in America where Diana still has a loyal following."

Meanwhile, Dame Helen Mirren - who won an Oscar for her portrayal of Queen Elizabeth in 2006 film 'The Queen' - has been named as a potential actress to play Diana's mother Francis Shand Kydd.