Butterfly follows separated parents divided over how to support their child, who was gender assigned male at birth but has identified as a girl from a young age. Star Anna Friel talks to Georgia Humphreys

ANNA FRIEL is used to being part of groundbreaking TV. Back in 1994, the Rochdale-born actress, 42, was one half of the first lesbian kiss to be broadcast before the watershed on British screens, in Channel 4 soap Brookside.

Her latest role, in ITV's Butterfly, sees her play the mum of an 11-year-old who was gender assigned male at birth, but has identified as a girl from a young age - a topic that has never been explored by a UK drama before. And she hopes the show can help change perceptions about transgender children in the same way that her lesbian kiss on Brookside did for all-female couples.

"I keep going back to 25 years ago when I was on Brookside and it was 'dyke, lezzer'... and now no one would blink an eyelid, no one would even think about that at all, it's the norm," she notes. "With any new topic that you're dealing with, you've got to think time changes everything. We all talk more, we discuss things..."

Butterfly, penned by Bafta award-winning screenwriter Tony Marchant, looks at a family in crisis - in particular, the complex relationship between separated parents Vicky (Friel) and Stephen (Emmett J Scanlan), as they work out how to support their youngest child, Max (Callum Booth-Ford).

Max identifies as female and dresses as a girl at home, but the social transitioning of Max to Maxine is initially thwarted because of the clear division of opinion between Vicky and Stephen. As their child's feelings become increasingly distressing, Stephen seizes the opportunity to return to live at the family home, with the hope of encouraging male bonding and proving himself to Vicky.

"To tackle something like this is a great responsibility but I think they've gone at the script really cleverly, because it's looking at it from every single person's side of it," suggests Friel, star of dramas such as Pushing Daisies, Broken and Marcella. The show, she says, examines: "What would happen to a regular normal working middle-class family that are just thrown into absolute disarray because they don't know what to do. And most people don't know what to do."

Friel is a mum herself, to 13-year-old Gracie, who she shares with her ex, Harry Potter actor David Thewlis.

"I said, 'This story is going to teach me something,'" she recalls of reading the script. "Because if this was my daughter Gracie, I don't know how I would deal with it. And I don't know what my views are because I'm so ill-informed.

"The he production company said, 'Well surely that's the reason to do this? That's what we want. We want people to question, open their eyes and not be ignorant'."

Filming the show was certainly an intense experience for both Friel and her co-star Scanlan, as they immersed themselves in the Trans community.

It was upsetting visiting Mermaids, a charity for children and families who are dealing with transgender, where they heard shocking stories of bullying.

"To be called a 'tranny' and a 'man-boy' or 'boy-girl', it's just awful, for any child. But it's more about the parents of some of the other children: 'We don't want them in our class, they might do something to our child'. Adults were being spat at and having death threats and you think, 'They're already going through utter trauma and you're just making this ten times worse'."

The star was asked if she wanted to be a co-producer on Butterfly, meaning she was involved from the very beginning, from casting, to working the scripts, and deciding how it was going to be shot.

"My first thing was, 'Well, why can't we get a real transgender child to play Max/Maxine?'" she discloses. "I was educated on the fact that it would really damage them, because in our story you've got to go from boy to girl and you'd be asking a transgender girl to go back to being a boy."

Discussing the challenges of the casting process, Friel adds: "Being a child actress myself, I wanted to make them feel as comfortable in the room as possible because I know the auditions are daunting even at this age. We'd go out and meet their parents, and think, 'What effect is that going to have on them, and are you ready to take this on?'"

Friel's first professional acting job came aged 13, in Channel 4's GBH (she played the daughter of Michael Palin's character). And she's positive about what roles are yet to come.

"There was a time of thinking in your head that, in your 40s, there are less women's roles available," she says. "But we've seen in the face of media that you don't just become boring and uninteresting because you turn 40. In fact, you actually become more interesting. You've got more life and story to tell."

She also knows the importance of having a break from work sometimes: after shooting ITV's Marcella for five-and-a-half months towards the end of last year she reveals she made herself have a "really disciplined" two weeks. "I didn't go out, I didn't see friends, I sat and thought to myself, 'Right, it's now time just to be a mother and be everything to your little girl'."

* Butterfly starts tomorrow on ITV.