The brief of Independent columnist  Grace Dent in this six-part series is to sit down with various Titans of recent BBC radio comedy and thereby sketch out its history between the somewhat arbitrary dates of 1975 and 2005. Episode one had her gamely colluding with Graeme Garden and John Lloyd, while episode two raided the memory kitties of Angus Deayton and Michael Knowles. By part three (15 November), she was encouraging the reminiscences of Hugh Dennis and Jim Eldridge, and the chronological clock had ticked forward to the late 1980s.And here we were back in the world of (mostly) alternative comedy, the self-­conscious, very slightly angry and over-loudly voiced universe of The Mary Whitehouse Experience and The Now Show, in which Dennis featured with his performing partner Ste