"I was walking along the beach and looked towards North Bruny and could see this massive bridge between Tinderbox and Bruny," Rose said.

"It was probably a trick of the light, but I started thinking about it."

This was in 2015 and the beginnings of Bruny had formed.

Not immediately recognising it at the time, Bruny's characters were already established in Rose's mind.

In fact, the Coleman family had been clamouring for attention since introducing themselves to Rose when she was 21, when she wrote a short story about family dynamics at a big festive event.

"I knew at 21 I couldn't do it, because I couldn't get the dialogue right," she said.

"They came back to me over the years and I wondered how the family worked. I felt familiar with the characters."

As an author driven by characters, rather than genre, Rose found herself writing about her home, but set Bruny in the near future at a time when global issues threatened to boil over.

"It was lovely to tell a global story through a local lens."

However, it was the character of Astrid Coleman, who came home to help her brother prepare for an election after a bomb exploded in remote Tasmania, who Rose got to know - and understand - the best.

Astrid's character, as she appears in Bruny, first presented herself to Rose in a vignette.

"I saw Astrid arriving at an airport. She was a petite woman and clearly well known, from the way people responded to her," she said.

A force to be reckoned with on - and off - the page, Astrid had Rose recoiling and laughing out loud in equal measure.

"I would write what Astrid was saying and thought I can't say that - I was mortified, but Astrid said it."

"She was an incredibly strong character to live with for a couple of years."

Rose usually starts a new novel with a scene at the beginning and end, and then has to "work out what's in between".

"I don't know what the story is. I have to follow the characters to work out what they have to tell me," she said.

"It's as much of an adventure for me as it is for the reader. It's like psychic orienteering."

Rose's writing process is "messy", with scenes and characters fighting for attention until they are fully formed.

"I found the same thing with The Butterfly Man - having a novel in my head is like having the radio on all the time. If I don't listen they get so loud," she said.

"I know it's done when I can't hear them anymore. Then it's a process of crafting.

"It's an exercise in surrender in so many ways."

Despite Bruny being Rose's eighth novel, it was the first she had written full time, after winning the 2017 Stella Prize and the 2017 Margaret Scott Prize in the Tasmanian Premier's Prizes for The Museum of Modern Love and receiving an Australia Council grant.

Bruny is published by Allen & Unwin on October 1.

As part of her publicity tour for Bruny, Heather Rose will be in Launceston at Petrarch's Bookshop on Thursday, December 5 at 6pm.

While you're with us, did you know you can now sign up to receive updates direct to your inbox?