December 29 1939. Listeners to the BBC on this evening caught the first work in the medium by that most British of American mystery writers, John Dickson Carr. "Who Killed Matthew Corbin?" appeared in three parts, running into January. It starred Gordon McLeod as Carr's sleuth Dr Gideon Fell.
Nu recordings are known to survive but Carr recycled the plot for "The Clock Strikes Eight," which you can listen to here.