Gabrielle Tana for Magnolia Mae and Michael Kuhn for Qwerty Films are producing with backing from Pathe Productions and BBC Films.
Bullet Boy's Saul Dibb is directing from a script by Jeffery Hatcher based on Amanda Foreman's biography Georgiana, Duchess of Devonshire.
The 18th century duchess, played by Knightley, was known for her beauty and charisma but was infamous for her extravagance with gambling and romance. Princess Diana was her descendent.
Pathe Distribution has UK and French rights, and Pathe Pictures International is handling international sales, starting pre-sales here in Toronto.