Born in South Africa, Langley was a novelist and playwright. His Hollywood screenwriting career began in 1936. He was chosen for the Oz project on the basis of his children's novel The Land of Green Ginger. He is credited with adapting L. Frank Baum's original book for the screen, and shares screenwriting credit with Florence Ryerson and Edgar Allan Woolf. In fact Langley had worked on his script alone, starting soon after MGM acquired the film rights from Samuel Goldwyn in February 1938.
When Langley completed his draft on 4 June 1938, he believed that he had written the final version of the movie. He was incensed when he learned that Ryerson and Woolf were doing another re-write. Arthur Freed considered the Ryerson/Woolf script too wordy, and brought Langley back to the project in August. Langley disliked the Ryerson/Woolf version; he found it "so cutesy and oozy that I could have vomited." Lyricist E.Y. Harburg backed and championed Langley with the producers. Langley cut Ryerson/Woolf materials from the script and restored as much of his own work as he could.
Among the fourteen or so writers who labored on the movie's script, Langley was one of the most important. It has been argued that the screenplay for The Wizard of Oz was in the main the work of Langley, Ryerson, Woolf, and Harburg. Langley contributed the idea of Oz as a dream; Glinda arriving in a bubble; and characters from Kansas (except Professor Marvel) reappearing in Oz in different guises. Langley was responsible for the film's dedication, for Toto discovering the Wizard behind his curtain, and for changing the book's silver shoes to ruby slippers (which looked much better in the Technicolor process used).
Langley's first response to the completed film was negative. "I saw it in a cinema on Hollywood Boulevard at noon. And I sat and cried like a bloody child. I thought, 'This is a year of my life.' I loathed the picture. I thought it was dead. I thought it missed the boat all the way around. I had to wait for my tears to clear before I went out of the theater."
Ten years later, though, Langley's opinion changed. He saw the film for a second time in England during its 1949 re-release. And then, "suddenly, I could see it objectively for the first time. And I thought, 'It's not a bad picture. Not a bad picture, you know.'"
Langley wrote a screenplay for a second Oz film, based on The Marvelous Land of Oz, which was never produced.
Langley continued to write for films, and later for television, after 1939. His career peaked in the early and middle 1950s, when he wrote the screenplay for Ivanhoe (1952), and both wrote and directed The Pickwick Papers (1952), Our Girl Friday (1953), Svengali (1954), and The Search for Bridey Murphy (1956).
- John Fricke, Jay Scarfone, William Stillman. The Wizard of Oz: The Official 50th Anniversary Pictorial History. Warner Books, 1989.
- Michael Gessel. "Langley's Screenplay for Wizard of Oz Sequel Discovered." The Baum Bugle, Vol. 42 No. 1 (Spring 1998), pp. 13-17.
- Aljean Harmetz. The Making of the Wizard of Oz. New York, Delta edition, 1989.
- Kenneth Von Gunden. Flights of Fancy: The Great Fantasy Films. Jefferson, NC, McFarland, 1989.