Peaky Blinders' star Charlotte Riley is to play the Duchess of Cambridge in a new BBC drama that envisions a constitutional crisis with Prince Charles as king.
Green Wing actor Oliver Chris will play Prince William opposite Charlotte, whilst Tim Pigott-Smith will star as King Charles III.
The inventive drama sees the new king refuse to sign a controversial bill causing political chaos, rioting on the streets and a tank in front of Buckingham Palace.
The 90-minute one-off programme is based on the Laurence Olivier award-winning 2014 play of the same name which also stars Tim and Oliver, as well as Richard Goulding as Harry and Adam James as the Prime Minister.
Charlotte said she was "excited" to play Kate, adding: "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.
"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."
Tim said: "Performing King Charles in Mike Bartlett's astonishing play in London and New York has been one of the high points of my career.
"I am thrilled that we are to film it - it is a drama about us, now, who we are, and the relevance of our monarchy. Television gives it an important democratic voice."
Directed by Rupert Goold, King Charles won the Best New Play at the 2015 Laurence Olivier Awards.
Writer Mike Bartlett said: "I couldn't be more excited that King Charles III is now fully, brilliantly cast and 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."