Lia's recent credits include acclaimed lead roles in the Almeida Theatre's Mary Stuart and Oresteia, The Missing Series 2 (BBC), and Wallis Simpson in The Crown (Netflix).
Dame Sian, who began her career in radio, is a legend of stage and screen, unforgettable in the BBC's I, Claudius, Marlene (Dietrich; by Pam Gems) in the West End and on Broadway, and most recently in Les Blancs at the National Theatre.
The production will be directed by Abigail le Fleming, and airs in July 2017.
