TWO brave victims of a vile Bonhill sex beast have spoken out on the impact of their stepfather’s attacks on them more than 40 years ago.

Sisters Mandy Duncan and Debbie Renwick were victims of paedophile Norman Duncan’s lewd, indecent and libidinous behaviour towards them at the family home between 1970 and 1976.

A jury took just two hours last year to find 71-year-old Duncan guilty of a series of sex offences against three girls.

The jury’s unanimous verdict was delivered after an eight-day trial at Dumbarton Sheriff Court in September, and two months later, the girls’ stepfather was jailed for five years for his crimes.

Now, both Mandy and Debbie have bravely agreed to waive their lifelong right to anonymity as victims of sex crimes after Duncan was this month refused leave to appeal against his conviction.

Mandy was attacked by Duncan on various occasions between January 1, 1970, and June 30, 1976, while the attacks on Debbie took place between March 1972 and June 1976.

Mandy was aged just five, and Debbie 10, when the attacks on them began.

Debbie said she hoped her stepfather's conviction on five charges of sexual assault on young girls might help bring the family closer to finding out what really happened to Mary.

And Mandy said she simply felt relief that the jury believed her story and not that of her stepfather.

Dumbarton and Vale of Leven Reporter: Norman Duncan

Norman Duncan, 71, has been jailed for five years for sex abuse crimes against young girls

Mandy's story:

“I ONLY gave my statement to police last February. I've got grandchildren of my own now and something inside me just clicked. I thought 'something's not right'.”

Mandy Duncan says her experience at the hands of her stepfather has left her unable to trust anyone.

Norman Duncan's attacks on her took place between January 1970, not long after her fifth birthday, and June 1976.

For 28 years, from 1976 until 2014, she didn't set eyes on her stepfather – or speak to police about what had happened to her.

But that all changed when she returned with her daughter to visit family in the Vale.

“My daughter said 'where does the dirty old b****** live?',” she said.

“We went to his door and I asked 'are you Norman Duncan?'. He said yes.

“I said the police were coming for him. He just backed away from me, going 'uh-huh, uh-huh'.

“He didn't deny what had happened. I think he was shell-shocked that I'd confronted him.”

Mandy, who has lived in Warrington for the last 28 years, eventually went to police in February 2016 to give a statement about what had happened to her at the family home 40 years before.

But she didn't see her stepfather again until the trial against him began last September.

“I never told the police everything,” she said. “What I told them was what I thought I could cope with.

“You learn to build a barrier round yourself for protection. I let my barrier down so far.”

Mandy said she didn't regret going to the police sooner to tell them what had happened to her.

“I don't think I was ready,” she said, “but obviously what I said was enough to help see him get convicted.

“I didn't go back again to confront him. I didn't really want to see him again.

“It felt as if I'd taken some of his power off him. He looked as if he'd just been hit by a spade.”

Mandy said she had to be prescribed anti-anxiety medication before giving evidence in the course of a day and a half at Duncan's eight-day trial.

“I was adamant I was taking the stand,” she said. “We just wanted it over and done with.

“After I gave evidence I was allowed to go and sit in the public gallery for the rest of the trial, but it wasn't nice listening to him saying Mandy's lying and Debbie's lying. He was just trying to get himself off.”

When the jury's unanimous guilty verdict on five of the charges against Duncan was delivered, Mandy shouted out in court that 'he's getting the jail'.

“It was just a relief,” she said. “It was important for me that it was a unanimous verdict.

“These people believed me. They believed what I'd said, and they believed what Debbie had said.

“Some people might wonder how I felt getting my dad sent to prison. But I didn't. He sent himself to prison.

“The way I looked at it was, he's a 71-year-old man with a bad heart. But he stole my life.

“He took my childhood away from me, so I've taken his last years away from him. I can live with that.”

Dumbarton and Vale of Leven Reporter:

A young Debbie and Mandy

Debbie's story:

Debbie Renwick can still remember exactly when she last saw her older sister Mary.

Born in January 1959, Mary disappeared in March of 1976, little more than a year after she gave birth to a baby girl, Laura.

“I can still remember Debbie leaving on the day she disappeared,” Mary said.

“We used to play out in front of the house, and I remember her walking past us and going down the wee brae.

“She had a navy skirt on – very fashionable in those days, an A-line midi skirt – green tights, very fetching platform shoes and was wearing what today you'd call a hoodie, and a black and white houndstooth jacket.

“We went to bed that night and never thought any more of it until the following morning.”

As far as Debbie is concerned, seeing her stepfather behind bars is just one more step on the road to finding out what happened to her sister.

But she also suffered at Duncan's hands – though it wasn't until the late 1990s that the painful memories she had buried away returned to her.

“I completely buried everything until I was in my early 30s,” Debbie said.

“I literally had no recollection of anything happening to me. I wanted to kill myself when I was 15, and I didn't know why.

“It came back to me in a flashback. I was cleaning a high school, and the radio was on, and a particular song came on and the memories suddenly came back to me.

“It knocked me off my feet a bit. I thought, how could I have forgotten that? Lots of things about my feelings started to make sense.

“I had to get a lot of counselling, and eventually I decided I needed to go to the police.

“I always had this feeling that somebody knew something about what had happened to Mary.

“This has always been about finding Mary. Don't get me wrong, it's a good thing Norman Duncan has been been found guilty.

“But finding out what happened to Mary has been the driving force.”

Dumbarton and Vale of Leven Reporter:

Mary Duncan was reported missing in 1976 and her sisters are desperate to find her

The family's sadness at Mary's disappearance was compounded when baby Laura died aged just 18 months after contracting bronchial pneumonia.

But that sadness sits alongside a lasting determination to find out what happened to Mary.

Debbie also took the stand to give evidence against Duncan – but even as she did so, and even on the days when he was found guilty, sentenced and refused leave to appeal, her focus remained not on her stepfather, but on her sister.

She said: “Even when I took the stand I was still thinking 'I'm doing this so I can find out what happened to Mary'.

“When the trial was over, and he was found guilty, as far as I was concerned that part of it was done. We were moving on. It was enough that he had been convicted.

“We were thinking 'what do we do now to raise Mary's profile? How do we try and see if there's anybody who knows anything?'”

But she hopes that her stepfather's time in jail will give him an opportunity to reflect on his actions – and to share anything he knows about what really happened to her sister all those years ago.

“I truly believe there's only one person now who knows anything about what happened to Mary,” she said.

“But I don't ever want to be face to face with Norman Duncan. If I was, all I would want to ask is 'what happened to my sister?'.

“I just think Mary shouldn't be lost. Right now she is still lost, and we need to find her. To really, properly, grieve, we need to find her.

“Until we do, we're in a kind of limbo. We get on with our lives, because we have to. But there's something missing.”

DCI Graham Cordner from Police Scotland's Argyll and West Dunbartonshire division, who is in charge of the investigation into Mary's disappearance, said: "I can confirm Police Scotland is still treating Mary Duncan as a missing person.

"We would welcome any new information from members of the public that could help us in our enquiries."