As a Screenwriter, he is notable for his collaborations with Martin Scorsese, particularly on the director's films The Age of Innocence and Gangs of New York — a screenplay he started working on in 1976 — as well as Kathryn Bigelow's Strange Days. He did an uncredited rewrite of James Cameron's screenplay for Titanic and was, with Scorsese, the co-screenwriter of Silence. Cocks and Scorsese approached author Philip K. Dick in 1969 for an adaptation of his 1967 novel, Do Androids Dream of Electric Sheep? Though the duo never optioned the book, it would later be developed into the movie Blade Runner by Screenwriter Hampton Fancher and Director Ridley Scott.
