Doctor Thorne actress Stefanie Martini is to portray a younger version of Jane Tennison, the role made famous by Dame Helen Mirren in Prime Suspect.
The forthcoming ITV prequel, titled Tennison, will see the 25-year-old take on the role of the Detective Chief Inspector.
Stefanie will be joined by The Riot Club's Sam Reid and The Inbetweeners' Blake Harrison, who will play her superiors DCI Len Bradfield and DS Spencer Gibbs respectively.
Alun Armstrong, best known for BBC One's crime drama New Tricks, is also set to join the cast, along with Unforgotten star Ruth Sheen and Medici: Masters Of Florence's Lex Shrapnel.
The six-part series - written by Prime Suspect creator Lynda La Plante - will focus on Tennison's early career in 1970s Hackney as a WPC, before she became one of the Metropolitan Police's first female DCIs.
Dame Helen played Tennison in the original ITV series from 1991-2006, a role which saw her win three TV Baftas for best actress.
Rada graduate Stefanie is best known for her role as Mary Thorne in Julian Fellowes' period drama Doctor Thorne; she also appears in TV shows Endeavour and Emerald City.
Filming has already begun on Tennison on location in London.