Just a bump of my own thread to note that the BBC genome project now has an extra feature - it shows links to the iplayer where a programme exists to be watched or listened to.
As well as the 7 or 30 day catchup service, the iPlayer has a number of collections of programmes that are available "indefinitely", and these are now indexed to the BBC Genome project.
Thus, if you search for "Desert Island Discs", you'll get links to the many editions that are available online.
Or, to just browse through what's available, click on advanced search, tick the "programme available" button and do a blank search. you can then sort by date, with oldest first.
Thus, the oldest programme available to listen to is part 3 of "The Sword in the Stone" from 25th June 1939, and it's quite fascinating to hear - the quality is impressive too.
BBC Genome
http://genome.ch.bbc.co.uk/Ian