National Theatre, LondonNiamh Cusack and Catherine McCormack perform the central roles with magnetic force in this frenetically comic adaptation of Ferrante's Neapolitan quartet At the start of the first novel in Elena Ferrante's Neapolitan quartet, its two young protagonists begin a fractious friendship by hurling each other's beloved dolls through a grille into a cellar controlled by the local loan shark, who lurks…