'Prime Suspect' prequel challenges star stepping into Helen Mirren role

However legendary a career becomes, everybody has to start somewhere ... even Detective Chief Inspector Jane Tennison.

The professional roots of the character created by Lynda LaPlante — and memorably played by Helen Mirren in the “Prime Suspect” dramas — are explored in the new PBS “Masterpiece” prequel “Prime Suspect: Tennison,” adapted from a 2015 LaPlante novel and beginning its three-part run Sunday, June 25. Stefanie Martini (“Emerald City,” “Doctor Thorne”) plays the title role, a police rookie circa 1973 here.

The year may be different, but the hurdles are similar for Tennison as she faces on-the-job sexism while trying to prove her capabilities. She finds a supporter and admirer in experienced detective Len Bradfield (Sam Reid) as she becomes involved in probing a young prostitute's murder and a crime-family patriarch's (Alun Armstrong) latest plot. Blake Harrison also stars as a temperamental police sergeant.

Martini admits to feeling “huge amounts of pressure” in following — or preceding, depending on your perspective — Mirren, who won an Emmy for the part. “But I think it's exciting to kind of have such an iconic role to kind of start from,” Martini says. “Jane Tennison in her 20s is very different to Jane Tennison in the last series, because she is young and naive and fresh-faced, so it kind of feels like a completely different character.”

Longtime “Masterpiece” executive producer Rebecca Eaton notes that while the new drama has a specific mystery, it also presents much about Tennison that's personal: “She's from a very middle-class, maybe even slightly upper-middle-class family, and she is assigned to a Hackney police station. And that was, in 1973, a really tough part of town. You get a lot more information in this about her parents, her sister, what they think of her joining the police. They don't support it. They don't think it's a good idea. They don't understand it.”

British native Martini was very aware of “Prime Suspect” when she went up for the part of Tennison, citing it as “such a huge thing in the U.K., you couldn't avoid it if you wanted to. It's brilliant. The audition process was, like, five months long ... so it was a lot of time to think about it. Once I knew I had the role, I watched most of 'Prime Suspect' again, and then didn't want to watch too much, in case I kind of became obsessed or something.”

Being a relative novice in acting, Martini relates to her Tennison being inexperienced in her job, too. “It's all pretty new for me, in the same way that for her, she's definitely learning and isn't experienced and makes mistakes. And then learns from them.”