Although this is an alert for a programme on R4 tonight at 8 pm, I include it in the R3 Arts thread as I think a lot of the archive material will have been taken from the Third (I heard some of his talks which were repeated on R3 in the 1970s and 1980s).
What I liked about his talks, apart from his very distinctive voice and clear prose style, was their range. They were not purely on philosophical matters, like his famous debate with Fr Copleston in 1948, but also extended to literature and the arts generally (as he knew so many artists). I particularly remember a talk about Joseph Conrad, whom Russell met and had long talks with.
Nowadays R3 has the Essay (and sometimes the Sunday Feature) as its sole representative of that fine tradition of talks given by people distinguished in their field, but it is a shame that it does not occupy a more prominent position and does not often attract philosophers, poets, playwrights etc.
It is also a shame that a programme about Russell and his involvement with BBC Radio should be on R4 rather than R3.