Stunning British actress Keira Knightley has warned her boyfriend Jamie Dornan to stay away from his co-star Kirsten Dunst.

The upcoming actor has landed a role opposite Dunst in the forthcoming film "Marie Antoinette", reports entertainment portal Hollywood.com.

The movie is based on the legendary French monarch and a courtier, played by Dornan, who was infatuated with the queen but his love went unrequited.

A production insider said: "It's quite a big role and we were very impressed by Jamie's audition. His character, Hans, is an admirer of Marie Antoinette. But Keira has made it pretty clear to Jamie that once the cameras stop, he's all hers."