Holliday Grainger has signed up to star in the BBC's adaptation of JK Rowling's crime novels.
Holliday, who recently starred in Lady Chatterley's Lover, has been cast as Robin Ellacott in the new BBC1 series, opposite Tom Burke as the detective, Cormoran Strike.
JK penned the Cormoran Strike series of novels - The Cuckoo's Calling, The Silkworm and Career Of Evil - under the pseudonym Robert Galbraith.
Holliday, whose credits also include Cinderella and Anna Karenina, will play the female lead in the TV drama, which begins shooting in London this month.
She said: "I'm thrilled to be joining the talented creative team behind the Strike series, especially with the role of Robin Ellacott.
"Her grounded strength and intelligence is going to be a joy to explore. I can't wait to dive straight into the wit and grit of Strike's cannily well-observed London."
Harry Potter author JK said: "I couldn't be more delighted about the casting of Holliday Grainger, who brought my Robin to perfect on-screen life during her audition.
"We've now secured two superb actors in the lead roles and I think they will create something very special together."
Holliday will play Robin, assistant to Strike, a private detective operating out of a tiny office in London's Denmark Street.
Though she starts work as a temporary secretary, managing Strike's chaotic life, she soon realises her full potential.
The Cuckoo's Calling was published to critical acclaim in 2013 and went on - after JK's identity was revealed - to be a bestseller, followed by The Silkworm in 2014 and Career Of Evil in 2015.
The BBC's adaptation of JK's 2012 novel The Casual Vacancy aired last year.
Tom's casting was announced in September.