Leone revitalised the genre of the western, sweeping away older conventions and deepening its moral complexity. As a young man he assisted de Sica, Donati and visiting American directors including Walsh (who told him the western was finished) and Wyler. Morricone, a crucial collaborator, had been a schoolfriend; Bertolucci and Donati also worked with him. Leone asked Mailer to help with a script before realising it was not his forte, and was warned by Welles against making one of his most memorable films. Scorsese, a great admirer, got his Sicilian mother to cook for him in her Lower East Side apartment.