Daughter of Sydney murderer Michael Caldwell reveals how she found out about her father's shocking past

Growing up, Saturday was little Renee's favourite day of the week.

Sneaking out early from school with her Nana every Friday afternoon, Renee McBryde knew the weekend meant she could listen to her dad's voice over the telephone.

Renee's father, Michael, "was very important" and "extremely busy" - meaning she had never actually met him in person.

From a young age, Renee had been told by her mum and Nana that he was the CEO of Cottee's Cordial - and "was so busy he was never able to leave the factory" where the drink was made.

So as a consolation, she got to speak with him - one on one - each weekend while she stayed over at her Nana's house.

After dinner and a bath, Renee would wait patiently for the phone to ring. While she was never allowed to pick up the receiver, she always knew it was her father on the line.

During their short conversations, talking about school, the playground and how her grandparents were going - her dad would often pass the phone around to his friends and colleagues that also worked at the cordial farm, and she'd listen to tales of how what a "top bloke" he was.

"I was obsessed with the Cottees cordial ad," Renee McBryde, who is now 34, told news.com.au.

"I used to sing the jingle to all my friends, and tell everyone how my dad was the boss of Cottees Cordial."

On one particular Saturday when she was just 6-years-old, the phone rang just before Young Talent Time started on the television.

After her Nana picked up the receiver and said a quick hello, Renee put her ear up to the headpiece and began her conversation.

But for Renee, on this particular Saturday night, the truth about who and where her father was, was finally exposed.

"He decided that it was time he told me the truth of where he really was," McBryde said.

"He told me he didn't work at Cottees, and that he wanted face-to-face contact with me, which couldn't happen unless I knew the truth about where he was."

Renee's father, Michael Caldwell, was calling her each week from jail. A convicted murderer - Caldwell was sentenced to life in prison for killing two men in Sydney in 1981.

At just 19, and working as a prostitute, Caldwell along with a 16-year-old juvenile were charged with the murders of Constantine Giannaris, Greek Consul General to Australia, and Peter Parkes, a gay activist and schoolteacher.

According to The Body Politic, Mr Parkes was murdered October 20 and Giannaris was found dead November 16.

Caldwell and his companion were arrested after police linked them with stolen jewellery belonging to Giannaris found in a Sydney pawn shop.

"The most overwhelming feeling was disappointment that he wasn't at Cottees," McBryde, who now lives in Alice Springs as a social worker, said.

"I didn't realise the gravity of what he was saying. I had an understand what jail was - but not in the way you do as an adult.

"I'd been lied to as a child, and that was the overwhelming thing, but I didn't completely understand he was confessing to a crime.

"But as I grew up and learnt more. I knew it was big deal what he had done."

Renee's mother Gemma, who fell pregnant with her when she was just 15, didn't know that the phone calls were taking place each weekend at her mother's house.

Following Caldwell's admission to Renee, her Nana was forced to tell her daughter what had been happening each Saturday night, and that 'the secret' had finally slipped.

"They started this lie because I was obsessed with the Cottee's Cordial ad," McBryde said.

"At some point they decided they'd just tell me dad worked there when I started asking questions.

"I genuinely believed that's where he was working."

Renee said that she felt the secret, and living a lie had a huge impact on her as a child - and into her teenage and adult years.

"I knew I couldn't say anything about me to anyone else, so I built a persona," she said.

"It took away part of my childhood, because I had to be so careful about what I said.

"With my mum, it was a sense of relief that I knew, because it meant she had someone she could talk to about it all. But that put me in a situation that was far to grown up for a child my age."

Growing up on Sydney's Northern Beaches, Renee was allowed to stay back with her Nan a few months after the truth surrounding her father dropped.

"He told me who he was because he wanted to see me face-to-face," McBryde said.

Living at Long Bay Correctional Centre, Renee's first visit to meet her father happened one weekend when she was eight-years-old.

"I was so overwhelmed, there were guards, and all I wanted a normal dad," she said.

"Then, when I arrived to see him, it hit me - he wasn't like everyone else's dad, and this jail was not the place for a child."

Over the years, Renee started uncovering more and more details into the exact reasons why her father was put behind bars.

When she turned 15, her father was out on weekend release - living in the Lower Hunter Valley of New South Wales.

"I went and visited him one weekend when he was out on release," McBryde said.

"I took the train from school to his house, where I met his new wife and new children.

"It's a tough time as a teen working out your identity even without all of this.

"It was such an awkward weekend. While he was welcoming, I was just so intimidated. I didn't realise the gravity of the situation. If you take the seriousness out of the situation, it was all quite comical.

"This played on my mind, and is what really pushed me not to let it impact me. I tried to outrun these parts of my genes. I wanted to go above and beyond, because I had more to prove."

Renee's experience and the devastating true story about her father, sexual assault, an identity crisis and the relationship she has with her parents today, is detailed in her new book The House of Lies.