A mother whose two young children were murdered by her ex-husband has revealed how her late son's final act of love 'saved her life'.Claire Throssell, from Penistone, South Yorkshire, suffered an unthinkable tragedy after her boys Jack, 12, and Paul, nine, were killed by their abusive father Darren Sykes during a court-approved visit in 2014.Sykes lured the children into the attic by promising them a new train set, but once the children were inside, he barricaded the doors, spread petrol around the house, and set it alight in 14 places. He died in the blaze together with his sons.Speaking in the latest episode of the podcast Our Key Witness: Aftermath, Claire revealed how her eldest son, Jack, 'saved her life' by outliving his evil father to ensure she would inherit the family home.She said: '[Darren] He did do exactly what he said he was going to do and take; he took everything away.'He'd put my address down, my mum's address and my name and said I was now responsible for the mortgage. But he knew that the house would be burnt to the ground by then.'It transpired that the only thing he hadn't done was make a will. So, Jack, at just 12 years old, saved my life because in the relationship, I'd separated the joint mortgage into a joint tenancy mortgage.'But that means only half of the house was mine. So, because Jack was his next of kin and outlived him, because it died three hours after the fire and Jack died five days later, he inherited half of the house. Claire Throssell (middle), from Penistone, South Yorkshire, whose two young children, Jack (left) and Paul (right) were murdered by her ex-husband, has revealed how her late son's final act of love 'saved her life''So because I was Jack's next of kin, that entire burnt out property became mine.'Last year, exactly 11 years after the tragedy, Claire was invited to 10 Downing Street after the Government confirmed plans to scrap the presumption that both parents should have contact with their children, regardless of concerns about abuse.The change, she said, meant her boys' deaths had not been in vain.Before the murders, Claire had repeatedly warned family court officials that her ex-husband posed a serious threat to her and their sons.She described years of psychological torment and controlling behaviour but her pleas for supervised access were ignored.A family court judge ruled that Sykes should have unsupervised contact, guided by the legal principle that both parents should remain involved in a child's life after separation.'I told the courts that he'd kill them,' she said. 'I told them what would happen. I couldn't predict how, but I knew he would do it.'Claire was at work when Sykes collected the boys for what should have been a five-hour visit. Their father had lured the children into the attic with the promise of a new train set before barricading them in and setting the house on fire Darren Sykes is seen with his sons, 12-year-old Jack and Paul, nine, who died following the house fire in South Yorkshire'I missed them by five minutes,' she said. 'I was late home, and I missed them for that last hug.'When she arrived at hospital, she saw medics battling to save her sons: 'His little body was bouncing off the bed' as they tried to resuscitate Paul, before doctors told her they could do no more.Jack died five days later from his injuries.Claire later learned that Jack had gone back into the flames to try to save his younger brother.After the tragedy, Claire began working with the domestic abuse charity Women's Aid, discovering that her sons were the 18th and 19th children killed by a parent during court-ordered contact.Together, they launched the Child First campaign to reform family courts and make child safety the top priority.