Two extremes of the listening experience were available on Monday on Radio 4. The day began conventionally enough with Start the Week, chaired by the deceptively genial Amol Rajan (now in charge of The Media Show), whose warm, inviting voice fronts a keen, intense intelligence. He guided his guests through a conversation about our post-truth world which, apart from the subject-matter, could have graced the airwaves in the 1950s.