Owen Marshall's new novel The Larnachs is based on an affair between the son and third wife of real-life 19th century Dunedin businessman and politician William Larnach. But how much of it is true?
"A writer of fiction has great leeway," says Marshall, "but I wasn't prepared to say that the affair at the heart of the novel existed if it didn't."
During his research for the book, Marshall found evidence to support the existence of an affair between Constance de Bathe Brandon and her stepson, Dougie Larnach, which has been suggested as a primary motivation for William Larnach's infamous suicide at Parliament in 1898.
The background for the affair - in the novel and in life - is the landmark Dunedin estate now known as Larnach Castle, though Conny and Dougie, who narrate Owen's tale, refer to it as the Camp.
Here, Marshall explains where fact and fiction meet in his novel, which has pushed Sarah Quigley's The Conductor off the number-one spot on the New Zealand fiction bestseller lists.

How did you come across the story of Conny and Dougie?
Over many years I have made occasional visits to Larnach Castle, and seen the gradual rehabilitation leading to its present splendid condition.
It has long been the focus of a swirl of fact, fallacy and rumour, and the affair between Conny and her stepson is part of that.

What was it about the story that captured your imagination?

William Larnach's life has an almost Shakespearian scope: everything about it on an epic scale, both success and failure, and ending in his dramatic suicide in a committee room in Parliament. His life is well documented, but there were other family members with different lives and untold stories, and they intrigued me as a writer.
How much of your story is based on verifiable fact? What were your sources for the factual element?
I found it substantiated in Fleur Snedden's 1997 biography of William, King of the Castle. She was a great-great-granddaughter of Larnach, and had access to family material. Later Michelanne Forster kindly allowed me access to information gathered in writing her successful play on the family. There is strong circumstantial evidence also. Such as Dougie supporting Conny against his brother and sisters in the legal battle over the estate, and the fact that after being evicted from The Camp, he moved to Wellington and lived for some years very close to Conny.
How did you handle stepping away from the factual into the imagined?
It's a matter of creating characters that are psychologically convincing within the slender framework of the known. Hopefully they develop an existence and credibility of their own, yet are still recognisably the historical figures. I emphasise at the beginning of the book that it is not a history, or a biography, but a novel.
The full interview at NZ Herald.