David Robertson, author of The Dawkins Letters, is due to visit Brighton in June/July. Yesterday he was on Premier Christian Radio's Unbelievable? programme, discussing the place of rationality, belief, progress and tolerance in a secular society, along with atheist blogger Adrian Hayter and Ariane Sherine, creator of the Atheist Bus Campaign. The fascinating conversation may he heard on the Unbelievable? page, on MP3, via the Podcast feed or on iTunes.