"Martin Wainwright asks who guards literary reputations after a writer dies? With Andrew Motion. From July 2003."

Includes Humphrey Carpenter talking about his Tolkien biography (starts at 7:50 into the programme and finishes at about 10:20).

I think you can listen to this world wide on the BBC iPlayer.

http://www.bbc.co.uk/programmes/b0076g3d