From the Chesterton and Friends blog:

As some Chesterton fans may recall, an earlier radio dramatization of The Man Who Was Thursday was broadcast on Orson Welles' Mercury Theater, September 5, 1938 (just a few weeks before Welles' famous radio recreation of The War of the Worlds). Frank Brady's 1989 biography, Citizen Welles, offers some interesting sidelights on this broadcast. Chesterton's novel was the last production of the Mercury Radio Theatre's inaugural season. Brady credits Welles' "splendid adaptation" of Thursday ("one of the finest shows of the season") with the last minute decision by CBS to renew the Mercury Theatre series. Furthermore, according to Brady, "Welles had great affinity for the works of Chesterton and decided to write the adaptation himself, allowing no assistance." [New York, p. 144]