But before he acted he had begged for help. He begged his psychiatric nurse, Margaret Stewart, to get him treatment. Five days before the Russell murders, she told police he had told her he was going to kill. Entry after entry in his medical notes included murderous threats, fantasies of torture, and names of those who had done him wrong.
There was no hospital place for him: the only bed that could be found was not deemed secure enough for such a mentally unstable man. And so, not for the first time, he slipped through the net. He was violent, suffered from a psychopathic personality disorder and had a long criminal record. Stone also had a pounds 150-a-day heroin addiction, a habit he fed by robbery and burglary.
He would steal from garden sheds, taking anything he could sell. Driven by his need for the next fix, his attacks became ever more violent, including mugging people at cash dispensers. It was a dangerous, volatile cocktail. On the fateful summer day when he drove 30 miles from his home to Chillenden in Kent and destroyed the Russell family in a 15-minute burst of violence, he may have been beyond treatment.
His acquaintances knew of his violence. As a boy he had been beaten with a hammer. Prone to uncontrolled outbursts and aggressive mood swings, he inhabited an underworld of squalid bedsits, further confused by his bisexuality. "When he's been violent towards me, afterwards he wouldn't remember doing it," said a former girlfriend, Rachel Marcroft.
Once Stone beat her so badly that she went to the police and they took photographs as evidence, although later she dropped the charges. "I had black eyes and my mouth was swollen and my neck was all bruised and my arms where he'd held me down. The police said the marks on me were similar to the ones on the lady that was found and that's one of the reasons [he was arrested]; they said the marks were too similar. I didn't even know they had kept the photographs."
Stone was born on 7 June 1960. His mother, Jane Standen, has been married four times, and he spent much of his childhood split between her home and that of the man he regarded as father, Peter Stone. There were also other men on the scene. One, Ivor Goodban, is named on Stone's birth certificate as his father.
Of Stone's four brothers and sisters, few will speak of him. Les Goodban, Stone's half-brother, barely admits he is related. "It is as if he has disowned him," said a family source. Stone was closest to his sister Barbara as a child, and he would grow explosively angry in her defence against the emotional and physical abuse that marked the family homes.
From the age of nine he was dabbling in drugs and crime. He soon came to the attention of the local authorities and spent time in at least four children's homes.
He may even have killed before. When he was arrested for the Russell murders he was questioned over the death of a former special constable, Francis Jegou, who died in a knife attack in Maidstone in September 1976, when Stone was 16.
What is known is that from his teens Stone spent most of his time in and out of Borstals, detention centres and jail. He has spent 17 years of his life in various institutions for offences including theft, robbery, malicious wounding and arson.
In 1983, he was banned for life for possession of firearms and jailed for four and a half years after he stabbed a man then attacked and almost blinded a policeman. Judge Felix Waley said: "I have ... to protect the public from you long enough to give you a chance to mature to some extent so that you are safe when you are out and don't resort to violence which might end with you killing somebody."
Yet the violence did not end. In 1987, he was sentenced to 10 years for the armed robbery of a building society in Brighton. Stone served five years before being released on parole. In jail he attacked a number of prison officers. He was also receiving attention for a violent personality disorder.
At the end of 1994, at the request of one of the doctors he was seeing, he was sent for assessment to the De La Pole mental-health unit in Hull. After two months he was again considered not to be suffering from a mental illness. Back in Kent he was again an out-patient.
His condition was controlled by regular medical injections, but sent haywire by the illegal drugs he used. "Sometimes his fix of heroin would be more important than getting his other injection," Ms Marcroft said.
On 4 July 1996, he went for an appointment at the Trevor Gibbons unit, where he threatened to kill his probation officer. Shortly before he was arrested for the Russell murders, he threatened to kill his sister Barbara and one of her children and smashed up her car.
But Anne Rafferty QC, the prosecutor during the trial, said that by July 1996 Stone's head had been taken over by thoughts of murder. He was in a "mood to kill". It was the Russells who suffered when Stone - psychotic, neglected and possibly even jealous of the happy family scene he had encountered - finally snapped.
As Stone began his life sentence, many questions about the murders remained unanswered. One detective said: "This is completely unlike any murder I have known in 20 years in the force. It wasn't domestic, it wasn't sexually motivated, it doesn't seem to be just about money. It looks as if Stone is mentally ill, but in one confession in prison he told someone he knew he could get himself nutted off [sectioned] if he was ever charged. It is difficult to know if Stone really has forgotten in a haze of drugs that he did it, and is mentally disturbed, or if he is just truly evil."Reuse content