Link: BBC World Service: “The Story of Africa: The Swahili” (HTML)
The link to the text article above is still good but the radio series, “The Swahili Coast” mentioned in the instructions appears to have been removed from the BBC website. Although it was old (being originally broadcast in 2002 I think) the links were still live about a year ago. It was a Real Audio streamed file and I suspect the BBC have now discontinued that format.
I have emailed the BBC and will update here should there be any good news.