To research The Perfumer's Secret, Fiona McIntosh learnt how to make perfume at the ancient perfumery, House of Galimard, in the town of Grasse in Provence, where her book is set.

McIntosh spent hours in the laboratory mixing essential oils to create an original perfume – tossing in notes of roses, violets with a touch of jasmine and the scent of tonka bean, ginger and green tea.

The resulting fragrance is named Fleurette​, in honour of her heroine, who within the first chapter walks down the aisle with a man she detests in an arranged marriage conveniently interrupted by the declaration of World War I.

McIntosh has taken vials of Fleurette with her on her Australian book publicity tour. The finished perfume harks to gentler times than the robust contemporary fragrances preferred by the prolific and hardworking author, who is just getting back on her feet after a bout of vertigo.

The Perfumer's Secret is the author's 30th book, and her seventh period romantic adventure. At any given time, McIntosh is writing a book, editing the galleys of her next-book-to-be-published and researching a third.

Her next novel is based in York, in northern England, and has chocolate as its theme. She is an addict of the gooey stuff, and loves to bake cakes. McIntosh concedes she may have to slow down in future but in the same breath raises the idea of writing an everyday cookbook and an account of her and husband Ian's recent decision to quit city life and shift to a tumbledown farmhouse on three hectares in South Australia's Clare Valley.

The most remarkable part of McIntosh's writing career is that she didn't start writing seriously until she was 40. The late Bryce Courtenay singled her out for praise when she attended one of his writing masterclasses.

It was the start of a mentorship that grew into an enduring friendship.

Courtenay's one piece of advice to McIntosh was that she should start writing fantasy fiction. He told her she wasn't ready to write epic period dramas. McIntosh rode the fantasy wave for 16 books. Thirteen years later Courtenay introduced her to Penguin, which published his annual bestselling fiction.

"When he was dying, Bryce called me to Canberra and wanted me there at his masterclass from the stand point of, 'Listen to me, you too, can be like Fiona'. I was to have been there for 90 minutes and stayed for the duration, tag teaming and helping him in every way to run the class, he was so ill. At the end of it, he said, 'Here's your new teacher'. As much as I didn't want to be, he literally made me promise to take over on his death bed."

McIntosh's breakthrough novel was The Lavender Keeper, and its follow-up The French Promise. Her readers were keen on a sequel but McIntosh didn't like the idea of setting a novel in the 1970s with its "black satin hotpants, hideous hair and dreadful sideburns". The Last Dance became a standalone novel that darts between London and Marrakech.

The Perfumer's Secret returns to Provence, a favourite playground. It was to have been solely about the making of a perfume until the idea of a revelatory letter came to McIntosh, turning the story's course "90 degrees". The book became this "sinful family secret that's reaching out from the previous generation certain to collapse the empire of this generation", she says.

McIntosh, 55, insists powerful, meaningful love stories lie at the core of her novels, not cliched romance.

"Not that I sneer at it," she adds. "I don't want to be pigeonholed with happy endings."

And yet all her male heroes are modelled on Mr Darcy. "They are actually Colin Firth in a wet white fencing shirt in Pride and Prejudice," says McIntosh. "Even though I hate those sideburns and that early 18th-century look, when he was in his fencing shirt and dived into that lake, women around the world lost their marbles, myself included."