“Elektra/Persona,” the U.K. National Theatre production fusing Sophocles’ “Elektra” with Ingmar Bergman’s “Persona,” grew out of friendship rather than a directorial concept imposed after casting, according to director Benedict Andrews.

Andrews, Cate Blanchett and Nina Hoss spoke at a BFI Southbank conversation held ahead of the play’s run, moderated by “The Guardian” chief film critic Peter Bradshaw following a screening of a restored 35mm print of Bergman’s 1966 masterpiece.

“Elektra/Persona” runs at the National Theatre’s Lyttelton Theatre from Aug. 19 to Oct. 10. In Sophocles’ “Elektra,” the title character mourns her father’s murder and waits for her brother, Orestes, to return and help her avenge it at the hands of their mother, Clytemnestra. In Bergman’s “Persona,” an actress, Elisabet, falls silent mid-performance and is sent to recuperate on a remote island, where a nurse, Alma, is assigned to care for her and the two women’s identities begin to blur. Andrews’ production stages “Elektra” in its first half and “Persona” in its second, with Blanchett and Hoss alternating between Elektra and Clytemnestra, and between Alma and Elisabet. The cast also includes Ella Lily Hyland. The production is staged by arrangement with Music Theatre International on behalf of the Ingmar Bergman Foundation.