<p>Returning to Birkenhead in the wake of Peter Sullivan’s release, we focus on Diane Sindall and the community still living with her murder. </p><p>Peter shares details of his arrest, interviews and alleged police pressure, alongside renewed police enquiries that revisit overlooked witnesses and potential suspects. </p><p>As officers collect fresh DNA and old memories resurface, the search begins anew for the man known only as 'Unknown Male One'. </p><p>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.</p><p>There’s graphic descriptions of violence in this series. For details of help and support in the UK, visit bbc.co.uk/actionline.</p>