A month before authorities uncovered Josef Fritzl's northern Austrian house of horrors in March 2009, Australian authorities had uncovered a virtual carbon copy of the nightmare scenario occurring in inner Melbourne.

Unlike what was happening on the other side of the world, there was no publicity for the woman who possesses only one photograph from her childhood and fell pregnant to her father six times - bearing four of his children, one of which died in infancy.

Instead, police quietly arrested a man in his late sixties for the rape, abuse and the imprisonment of his only daughter.

Now, six years on, Katherine X has finally spoken out about her lifetime of fear and abuse at the hands of her father - the man who was meant to protect her, not prey upon her.

Last month, Katherine gave evidence before the Royal Commission into Institutional Responses to Child Abuse under the name BGD.

Her true identity can't be revealed, as she has not yet told two of her sons that their grandfather is actually their father.

Principal Commissioner Bernie Geary told A Current Affair he was shocked and saddened by Katherine's life and believes she is an inspiration for other survivors of child sexual abuse.

"She's probably the bravest person I've ever met," Mr Geary said.

"We use the word resilient really lightly in our sector, but Katherine really is the personification of resilient for what has happened to her," he said.

The sexual assault started at 12 and at 25, Katherine had her first child - a boy.

"It was always put down to me, as my fault," Katherine told A Current Affair .

"He wouldn't acknowledge that that was his child. He would say, 'It can't be, I'm sterile'," she said.

Even after Katherine gave birth, the abuse continued.

At 27, Katherine had a miscarriage. At 31, she had another miscarriage. At 33, Katherine gave birth to another son. At 35, she gave birth to a third son. And at 36, she had a daughter - who died after 12 weeks.

But it took 27 years for authorities to act - despite Katherine reporting it to social workers and police officers at least 22 times.

The twenty-third person she told was a social worker, who told the twenty-fourth person - Senior Constable Danny Shaddock, of Victoria Police.

Senior Constable Shaddock then did what no one else had – he investigated the claims and DNA tested Katherine's three sons.

Finally, after almost 30 years, Katherine's father was charged with 83 separate offences.

Those charges were condensed into 13 charges when he appeared before the Victorian County Court - with one of those charges alone containing 700 counts of rape.

The sentence for 27 years of physical and psychological torture against his own daughter: 22 years.

With her father behind bars, Katherine wants her story told.

Australian Women's Weekly senior journalist Sue Smethurst obliged and in May, released the book Behind Closed Doors .

"There was no escape for her - every house she lived in held the darkest of secrets. She was a prisoner in her own home and even though there were no bars on the windows, she was his prisoner, he controlled every aspect of her life," Sue Smethurst told A Current Affair .

But despite her dad now being behind bars, Katherine still doesn't feel free.