A 19-year-old trainee accountant described by doctors as Britain's most dangerous teenager was sentenced to life on Friday after being found guilty of stabbing a nurse to death in a frenzied attack as she took a cigarette break last year.
Stuart Harling, who had told the Old Bailey he had rape fantasies and had wanted to carry out a gun rampage at a school where he had been bullied, said he murdered Cheryl Moss, 33, because he was bored.
The former scout leader and school prefect had surfed Web sites featuring murder, pornography, knifes, guns and serial killings.
In sentencing, Judge Brian Barker said: "This in itself would be cause for concern but the evil is you put your research into practice and Cheryl Moss had the misfortune to stumble across your path."
He added: "Your destructive and deadly actions appear to have meant little to you.
"What you have gained, and what you have sought, is infamy."
He said Harling's actions had robbed the community of a vibrant and contributing member of society.
Harling, wearing a fancy dress witch's wig and dark glasses, stabbed Moss 72 times with a hunting knife in a savage attack outside St George's Hospital in Hornchurch, Essex, in April last year.
The attack was so sudden she did not have time to scream and he only stopped stabbing his victim because his wig fell off.
"I cannot think of a more dangerous teenager in the country," said Dr Philip Joseph, one of the country's top consultant forensic psychiatrists.
He questioned whether it would ever be safe to release Harling and advised extreme caution when considering release.
"Harling comes across as a well balanced, polite individual which may mean he will be eligible for parole early," he said.
"On the face of it there is nothing about him that would alert you to how dangerous he is."
Police believe that Harling was a serial killer in the making.
He had admitted killing Moss, who had worked at the hospital for more than 10 years, but denied murder on the grounds of diminished responsibility.
Under cross-examination, Harling said he had wanted to carry out a shooting similar to the massacre at Columbine High School, Colorado, in April 1999 when two students shot dead 13 people and then killed themselves.
"Harling was obsessed with being notorious and with serial killers," said Detective Sergeant Elaine Pugh.
The court heard that Harling suffers from Asperger's syndrome and also has a schizoid personality disorder.
Prosecutor Brian Altman said: "This murder was not a spontaneous act -- far from it. Inflamed and fuelled by the fantasy world he lived in, he developed a plan over time, a plan to kill someone which he executed in a chillingly cold blooded way," Altman said.