McKenzie, who is best known for her roles in "Cranford" and "Notes on a Scandal," is to play Miss Marple next year in three episodes of the fourth season of the show based on Agatha Christie's mystery novels. She takes over the role from actress Geraldine McEwan who retired after wrapping the third season.

"For me, Julia ticks just about every box when it comes to playing the Marple character and I'm thrilled that she has agreed to take on this new challenge," Phil Clymer, director of TV and film for Chorion, which owns the rights to the Christie brand, said in a statement.

David Suchet is to reprise his signature role as the Belgian sleuth Hercule Poirot in two new episodes of "Poirot," as well. The star of all but 12 adaptations of Christie's best-selling Poirot books, Suchet was recently in the feature film "The Bank Job."

Agatha Christie's "Miss Marple" and "Poirot" are co-productions of ITV Productions and WGBH/Boston in association with Agatha Christie Limited, a Chorion Company.

Both shows are to air on PBS as part of the station's Masterpiece Mystery programming.

Masterpiece has been presented on PBS by WGBH since 1971.