Helena Bonham Carter in The Guns of August
The film is based on the Pulitzer-winning book by Barbara W Tuchman and depicts the detailed build-up to the outbreak of the First World War, while examining the intricacies of a family dispute which had such wide-reaching consequences.
Bonham Carter will play Margot Asquith, who was her real life step-great grandmother. Charles Dance and Emilia Clarke also star. Oliver Hirschbiegel directs from a screenplay by Rainmark's Frank Doelger, whose producing credits include Game of Thrones, John Adams and Rome.
Filming is expected to be underway early next year on the period feature. Bonham Carter first has to shoot Through the Looking Glass, with Johnny Depp and Mia Wasikowska.