5. Unknown Male One

Recorded on the day of Peter Sullivan’s appeal as judges consider DNA evidence unavailable in 1987.

As the new evidence points to an unknown male, decades-old evidence crumbles under scrutiny.

The court delivers its decision leaving one devastating truth intact: Diane’s killer has not been found.

Presenter: Olivia Graham.

Producers: Kate Bissell, Gemma Maull and Olivia Graham.

Sound Design and Music Composition: Phil Channell.

Mixing: Ivan Eastley.

Story Consultants: Neil McCarthy, Jack Kibble-White and Kirsty Williams.

Online Producer: Rachael Smith.

Development was by BBC Audio Scotland and BBC Merseyside.

Executive Editors: Gillian Wheelan and Ben Anderson.

Commissioning Editor: Alistair Miskin.

There’s graphic descriptions of violence in this series. For details of help and support in the UK, visit bbc.co.uk/actionline.