Stefanie Martini to play Jane Tennison in Prime Suspect prequel

Martini also featured in Endeavour, the Inspector Morse prequel

Doctor Thorne actress Stefanie Martini has been cast as a young Jane Tennison in a prequel to popular crime drama Prime Suspect.

Tennison will tell the story of the early years of the character made famous by Dame Helen Mirren.

The cast also includes veteran actor Alun Armstrong as the head of a crime family and The Inbetweeners star Blake Harrison as DC Tennison's sergeant.

An ITV spokeswoman said filming had begun on six hour-long episodes.

Martini tweeted that she was "so happy" to be able to announce her involvement in the series, written by Prime Suspect creator Lynda La Plante.

The role of Jane Tennison was originally played by Dame Helen Mirren

Other cast members include Australian actor Sam Reid as Tennison's inspector and Geraldine Somerville and Nick Sidi as her mother and father.

The spokeswoman said the show would look at the beginning of Tennison's career, "revealing why she became such a complex and formidable character in the Metropolitan Police".

The Tennison prequel follows the success of Endeavour, which tells the story of Inspector Morse's early years in the police. The drama, which featured Martini, recently announced a fourth series.

No transmission date for Tennison has been given.