Guest Stars El Anthony as Mark De Costa Jonah Collier as Young Robert Napper Deka Walmsley as DCI Mick Wickerson Anya Cooke as Young Napper's Sister Natasha Jayetileke as Newsreader Jack Riddiford as Robert Napper Anna Tierney as Samantha Bisset Simon Kunz as Justice Ognall Jasper Jacob as John Nutting QC Simon Armstrong as SIO Micky Banks Crispin Letts as Psychotherapist Adam Loxley as Camping Man Susan Gillias as Female Prison Officer Mark Ellul as Prisoner 2 Michael Ukandu as Prisoner 1 Alexia Russell as Jazmine Bisset Nick Malinowski as DS Alan Jackaman Simon Wilson as Jim Sturman QC Bruce MacKinnon as William Clegg QC