Leading ladies Charlize Theron and Carey Mulligan are reportedly on the short list to play the ultimate leading lady -- Princess Diana.

A new movie about the late princess is in the works, based on the 2007 book Diana: Closely Guarded Secret, written by Di's bodyguard Ken Wharfe.

Producer Stephen Evans, currently basking in the success of The Iron Lady, was keeping mum on casting. 

“It’s a ­slightly closed book until we get her," he told the Sunday Mirror. "We are ­looking at one or two ­relatively unknowns we think could play Diana well, and also one or two very famous ­people."

Ewan McGregor is rumored to be in the running to play Wharfe.

Evans said the film will cover 11 years in the life of the princess, starting shortly after the birth of Prince Harry and leading up to Diana's 1996 divorce from Prince Charles. The movie won't dish on any of Di's personal relationships or conspiracy theories about her death, Evans said.

"The emphasis on this really is authenticity and to discover what she went through," Evans told the paper. "Unless you are a Diana freak, quite a lot of it will be unknown to the audience.

"The movie's not saying she is unbelievably wonderful or she's a pain in the neck. The audience can make their own view."

Tags: Charlize Theron Carey Mulligan