Langley was a writer, dramaturge, screenwriter and director. He began his career as a writer and dramaturge on Broadway. In the mid-1930’s he began writing screenplays for films. One of his first was the adaptation of The Wizard of Oz (1939). He was chosen as a collaborator on that film thanks to the success of his story for children The Tale of the Land of Green Ginger. His screenplay was later modified, which he did not agree with, and even though the film was a huge success, Langley said that after the first time he saw it, he did not like the film at all. Later he tried writing the screenplay for its sequel but the film was never actually made. After WWII, he worked as a screenwriter on British films They Made Me a Fugitive (1947) by the director Alberto Cavalcanti, Tom Brown's Schooldays (1951) by Gordon Parry, Scrooge (1951) by Brian Desmond Hurst and Ivanhoe (1952) by Richard Thorpe, which were all film adaptations of famous novels. He wrote the screenplay based on Dickens’ first novel The Posthumous Papers of the Pickwick Club and decided to direct it himself, so he made The Pickwick Papers (1952). Then he wrote the adapted screenplay and directed Our Girl Friday (1953) starring Joan Collins. A year later, he did Svengali (1954). The last film he directed was The Search for Bridey Murphy (1956). After that, he continued working as a screenwriter for film and television, writer and dramaturge.