For a brief few weeks around the close of 2014, it felt as if you could divide your acquaintances into two groups: those who were listening to Serial and those who were not. Devotees of this spin-off from the popular podcast This American Life soaked up the insistent, questioning voice of investigative journalist Sarah Koenig as she unpicked the frayed ends of a true-life murder case. But, beyond the fascinating, disturbing facts it forensically investigated, Serial’s enormous popularity suggested that the spoken word might have become the ‘new rock and roll’.