Sarah Koenig's Serial has turned the podcast into an art form

Even those of you who only listen to traditional “linear” radio – who wouldn’t know a podcast if it broke into your house, smashed up your trusty Roberts, jammed a pair of headphones onto your head and pressed Play – even you must have heard of Serial. Season one, released in 2014, was the first podcast to bust through the membrane of cult listenership and become a mainstream phenomenon. It has since been downloaded more than 170 million times, won all sorts of awards and created a template for a new kind of investigative journalism.