"The Bea Smith in Prisoner was always in prison so you never saw her before that. Setting this series now but also going back and watching that journey is interesting as people know she becomes top dog at some point."
Sentenced to life without parole for the murder of the drug-dealer she holds responsible for her daughter's death, the opening episode of the new series finds Bea adjusting to her newfound status as the influential kingpin of the prisoners.
"Now that we've arrived at that point and are able to tell that story, people are going 'what are you going to do with her now that she's top dog?' which is what season three explores," says Cormack.
"In season two, Bea was granted revenge on Brayden Holt, so where is she going to go now? What happens next now that has all been achieved?"
According to Cormack, Bea's vendetta against Brayden Holt has inevitable consequences for her relationships with some of her fellow inmates.
"She is aware that she has compromised some friendships to get what she wanted, which is like a brutal slap for her," she says.
"She has to pay reparation for that and she also now has the great responsibility of leading the women, which brings out her maternal side again as she tries to affect change and look after the women. She tries to eliminate certain dangers and still hold her ethics in place, which she finds virtually impossible to do."
Admitting that, "it's been busy for me", Cormack has found herself in almost constant demand since relocating across the Tasman in 2007. Having appearing regularly in Underbelly: Razor and Rake, Wentworth has really put her on the Aussie acting map.
The most watched show in Australian pay channel Foxtel's history, is rapidly increasing in popularity in the UK and the US - where it screens on Netflix - and indeed New Zealand.
"There's a lot of similarity between the two countries but there's a lot more people in Australia so they produce more product, which stands to reason with a greater population," she says of her big move.
"Australia has been wonderful to me with the work I've had there, as I've been given some pretty significant roles in the three series I've been involved with. They've also been pretty well received critically and - apart from Underbelly - have all gone on for more than one series. And season four of Wentworth, has just been commissioned."
But despite her two decades in the New Zealand acting industry before shifting to Australia, Cormack had never previously worked with Kiwi-Samoan actor, Robbie Magasiva, whose put-upon prison guard Will Jackson returns from his controversial suspension at the start of series three after becoming inadvertently embroiled in Bea's scheme for vengeance.
"Robbie's great but it's been really good working with everyone on the show, as they're a bright, brave bunch of actors," says Cormack.
"After working for three seasons on a show, you become really close. And not just with the other actors but also the crew, as we've had a relatively smooth continuity of people."
Citing fellow prison drama Orange is the New Black, Homeland and BBC series The Honourable Woman, Cormack believes Wentworth is a crucial example of a growing trend for television series that focus primarily on women.
"A big part of the show is that it has a predominantly a female cast, who deal with female issues," she says. "Of course, you're going to have male guards in there, so they bring in that element of romance and gender politics.
"But being a predominantly female show is extraordinary, as it doesn't happen often. Thankfully people are starting to produce shows that explore women in a much more in-depth way, where you're not just playing the wife, a lover or the mother."
• Wentworth returns tomorrow night at 8.35pm on TV2.
