EXCLUSIVE: The Affair star Ruth Wilson is the latest A-list star to sign up to BBC drama His Dark Materials.

The actor is signing up to play Marisa Coulter, one of the main protagonists of the eight-part drama and the former lover of Lord Asriel, played by James McAvoy. The character is one of the main characters in the trilogy of novels written by Phillip Pullman, particularly The Amber Spyglass, the third novel, where the character is described as a beautiful 35-year old.

She is thought to be the mother of Lyra, played by Dafne Keen, who has a golden monkey demon.

This comes after X-Men and Atomic Blonde star McAvoy and The Wire’s Clarke Peters  signed up to star in the drama.

His Dark Materials, which will air on BBC One, is written by National Treasure and Wonder writer Jack Thorne. It is based on Pullman’s trilogy of books: Northern Lights, The Subtle Knife and The Amber Spyglass, a complex tale of physics, philosophy and theology featuring witches and armored polar bears. It tells the story of two children, Lyra and Will, who wander through a series of parallel universes.

Earlier this year, Deadline revealed that The King’s Speech director Tom Hooper is to direct the series, which will also star Lin-Manuel Miranda as adventurer Lee Scoresby. It will be exec produced by Hooper, Pullman, Tranter, Gardner, Toby Emmerich and Carolyn Blackwood for New Line; Piers Wenger and Ben Irving for BBC One and Deborah Forte for Scholastic.

Bad Wolf and distributor BBC Worldwide have also been talking to a number of international broadcasters and streaming services about the project, which is thought to be one of the most expensive British dramas to date. Apple and Netflix are among the suitors for the U.S. and global rights. Endeavor Content co-reps North American rights with BBC Worldwide.