NEITHER the reading nor the writing of detective novels is any longer regarded as an occupation beneath the notice of the learned, and Mrs. Cole, the daughter of a Professor and the wife of a Reader in Economics at Oxford, has been partly responsible for some of the most popular mystery stories of recent years. Moreover, her collaborator is her husband, Mr. G. D. H. Cole , the expert on the history of the trade unions. Later in the autumn a story by these two writers is to be serialized over the microphone, listeners being invited to try their hand at the solution of the mystery, and particular interest therefore attaches to this evening's talk.