Guest Stars Kevin McNally as Professor Peter Cherry Emily Piggford as Professor Elizabeth Newport Kaye Wragg as Valerie Fullerton Maeve Courtier-Lilley as Vanessa Miller John Thomson as DI Warren Bull Ashley Margolis as Haidar Alam Diveen Henry as Elaine Robinson Richard Keep as Harrison Cairney Isobel Wood as Celeste Locke Julie Jupp as Woman with Dog Harry Lister Smith as Homeless Man James Craze as Roy