Actor Sonia Todd to lead cast in Canberra stage adaptation of Frank Moorhouse's novel Cold Light

Cold Light, by Frank Moorhouse, that is itself the third instalment in an epic trilogy, will finally reach the stage next year, having been adapted for Canberra theatre company The Street Theatre by playwright Alana Valentine and tested by various audiences throughout the drafting process.

But, director Caroline Stacey says, now that lead character Edith Berry has been cast, the stage, as they say, is set for rehearsals to begin in earnest.

"I have to say though, once we cast Edith, it was like a lot of stuff just settled, because there'd always been that question mark over who is going to actually manifest and realise this amazing character," Stacey says.

"She is very flamboyant, quite unconventional and there's a bit of emotional range and landscape. She's a compelling character, a good character to get your teeth into, but not a character that maybe everybody would feel comfortable playing, and so the process of sending the script, sitting down, having a conversation, looking at how it feels, and building an ensemble around that central character – it's quite a complicated process."

Enter Sonia Todd, a veteran Australian actor of stage and screen, beloved of Australian television audiences thanks to her roles in McLeod's Daughters and Police Rescue. Stacey says Todd is the perfect actor to embody the role of Edith, a complex, flawed protagonist.

"She's not a character that necessarily has absolute agency, she's not a Xena Princess Warrior taking on the world and beating down doors, it's much more complex and nuanced than that," Stacey says.

"It's fantastically rich, complex, difficult, and I'm having lots of sleepless nights over it. It's all-consuming, just thinking about those lines into the work, and also what it reflects back to us in terms of – the city we have now is very different from the imagined place, when Walter Burley Griffin and Marion Mahony had that initial vision, and then what happened through all the filters of people through the last 100 years."

Set in Canberra in the 1950s, Edith is out of work, having been part of the now-collapsed League of Nations. She fetches up in the fledgling capital with dreams of becoming Australia's first female ambassador. Instead, she finds herself caught up in the planning of the city and all that entailed in a city still emerging from the doldrums of World War II and the Great Depression. Moorhouse researched it for years, and when the idea came about that it could be adapted for the stage – a Canberra Centenary legacy project instigated by his friend and Centenary creative director Robyn Archer – he insisted that the playwright be a woman.

Award-winning playwright Valentine was the perfect fit, creating a work that is at once dense and poetic, staying true to the hefty novel while still whittling down the story to its essence. Much of which, says Stacey, is embodied in the character of Edith.

Todd says the role resonates with her deeply.

"I think as an actress, you have to be able to connect, at least in some way, but I connect with Edith in so many ways," she says. "I really enjoy that idea of wanting to make a difference, to be significant, to be able to share, to show off, the talents and abilities that you have, and to feel that you still have something to offer the world at large.

"And I think for an actress that isn't a young actress in her 20s, where the quest is very evident, to be able to have that quest is just something that is fantastic for an actress like myself to be involved in."

Todd was drawn to both the "purity of Edith's drive" and her emotional layers.

"I think she is definitely complex, but I love the simplicity of what motivates her, though, so she does do contradictory things, she doesn't always take the easy road, and then when she has got something good in her life, she sacrifices it to get what she feels she wants," she says.

She is also attracted to the story's 1950s aesthetic, one that goes far beyond just Mad Men-style costuming and quaint dialogue. It's a sensibility that requires tapping into, and not all actors would be up for it.

"It's interesting because I've heard some people of my parents' generation say it was a fantastic time, it was really wonderful, there was so much opportunity, there was happiness in the air, there was colour and all that sort of thing," Todd says.

"Some people had a fantastic time, and other people thought it was deadly dull, and it mentions in the play as well the role of women needing to change after the war and what was required of women to do with their lives for everybody to fit back into a way of being after two wars and a depression, specifically the Second World War and the way the country was blossoming, the potential of the country and what was expected of women. And Edith has none of that – she has her own agenda and her own thoughts on things and the way things should be, could be."

Stacey says getting the play right is a huge responsibility, not least because many readers have convinced themselves that Edith is a real character.

"It [also] tells another story of Canberra, and it becomes part of reframing that history, that language," she says.

"I feel every time works like this are done, there's adding and chipping away at stereotypes and adding dimensionality and character and ownership to our story here in Canberra. And that's actually the power of theatre and the arts. We can change that story more so than any marketing campaign. Because obviously works of art remain.

"It's soft diplomacy in action and the best sort, because you're paying artists and creative people to make fabulous work."

The Street Theatre will present Cold Light, starring Sonia Todd, in March 2017.