Why has the city of Oxford produced some of the world's most famous fantasy writers for children? Radio 4's Michael Rosen is joined by Phillip Pullman, Jonathan Miller and AN Wilson as he explores the nooks and crannies of medieval buildings, rifles through dusty papers and climbs into hidden hide-aways to try to explain it. The programme is on at the moment (11.30GMT) and repeated on Monday at 12.45AM. It should appear here to listen again too.