Hermione Norris is joining the cast of BBC One spy drama, Spooks.

The actress, best known for her role as Karen Marsden in Cold Feet, has agreed to play tough MI5 agent Ros.

"Ros is much nastier than anyone expects and really shakes up the team," a source told The Mirror. "Producers hope she will give the show more of an edge."

Norris's first episodes will air late next year.