Interestingly, when Lewis was asked to be on the air (this was done by letter), no one at the BBC had heard him speak. It was hoped that because someone there enjoyed the clear writing style in The Problem of Pain that he would be a good candidate for a special short series of talks. So, one hot summer evening in August set the stage for Lewis to become well-known from being on the radio. Later this talk became the first chapter in Mere Christianity that was released in 1952 (along with material from three other radio series he did). But in the early 1940’s it was known in the U.K. as being a part of Broadcast Talks and in the U.S. when it was released it was called The Case for Christianity. Of course, Lewis’s fame would rise even higher as beginning in 1950 a new story from The Chronicles of Narnia was published annually for seven years.
You can learn more about this in a special blog post at C.S. Lewis Minute.