It’s a brave dramatist who would seek to adapt for radio the hit novels of the Italian writer Elena Ferrante. As soon as her quartet of novels set in Naples from the 1950s onwards began appearing in English translation a few years ago they created a bestselling stir because of the unusually bold flavour of the writing and the brutal honesty with which Ferrante is prepared to expose the dark underside of female friendship and motherhood, its jealousies and bitterness, the betrayals and self-centredness.