Peaky Blinders actress Charlotte Riley has been cast as the Duchess of Cambridge in the TV adaptation of the award-winning play King Charles III.
The play, written by Doctor Foster writer Mike Bartlett, is being adapted into a one-off drama for BBC Two.
The Olivier Award-winning play imagines Prince Charles's accession to the throne following the Queen's death.
Tim Pigott-Smith, who played King Charles on stage, is reprising the role for TV.
Charlotte Riley, who has also appeared in the mini-series Close to the Enemy and the film London Has Fallen, said she was "really excited" to take on the "challenge" of playing Kate Middleton.
She said: "It's such a unique project. To be both modern and rich in verse and to play someone who is real but yet totally re-imagined for this story is an exciting prospect for an actor.
"Kate Middleton is a really interesting woman, particularly within the context of this play, and it is a challenge I am really looking forward to."
In the play, King Charles refuses to sign a controversial bill into law, leading to political chaos, a constitutional crisis and rioting in the streets.
Pigott-Smith said it was important that the play, which also transferred to Broadway, was filmed.
"It is a drama about us, now, who we are, and the relevance of our monarchy," he said. "Television gives it an important democratic voice."
Other cast members from the stage version also starring in the adaptation are Oliver Chris as William, Richard Goulding as Harry and Margot Leicester as Camilla.
Bartlett said the production was now fully cast and is about to begin shooting.
"We have an exceptional team, both in front of and behind the camera, and I'm looking forward to bringing this very contemporary royal tragedy to a national television audience," he said.