Heath Ledger’s Joker was based on a Francis Bacon painting, says Christopher Nolan

Exclusive: Hollywood director is one of several leading creatives to speak of Bacon’s influence ahead of an exhibition at the National Portrait GalleryHeath Ledger’s portrayal of the Joker was based on one of Francis Bacon’s triptychs, the Oscar-winning director Christopher Nolan has revealed ahead of a new exhibition of Bacon’s work.Nolan is one of several leading creative figures who have spoken of Bacon’s influence on their life and practice to mark the opening o