Perhaps not since Jack the Ripper prowled the streets of London has there been a killer as depraved as Robert Napper.

Yet until now he has been denied notoriety because of an overreliance on criminal profiling combined with the police’s fixation on jailing another man for his most notorious crime — the murder of Rachel Nickell.

Napper terrorised as many as 86 women in a series of assaults in south-east London, known as the Green Chain attacks because of their proximity to a walking route of that name. They escalated, as he became more deranged, from indecent exposure to the rape of a mother pushing a pram.

When the police attention on his “hunting ground” came too close, he crossed London to kill Ms Nickell as she walked on Wimbledon Common with her son, Alex, aged 2. While the hysterical child looked on, Napper stabbed the mother 49 times and mutilated her body.

In November 1993 he broke into the flat of Samantha Bissett and stabbed her to death before sexually assaulting and smothering her four-year-old daughter Jazmine. He then returned to Ms Bissett’s body, which he mutilated with macabre precision.

To date, seven crimes can be firmly attributed to Napper — three killings, two rapes and two attempted rapes. He refuses to discuss any further cases unless police can produce scientific proof of his guilt.

He is likely, regardless of future prosecutions, to die in Broadmoor. It was recently claimed however, that inmates at the high security hospital’s Paddock Unit, where he will probably be housed, were pampered. Lee Porritt, a former inmate, said they had flat-screen televisions and stereo systems in their en-suite rooms.

Napper’s trademark was attacking young mothers with children. Psychologists put the trait down to a childhood scarred by abuse and violence,

He left a trail of fingerprints, footprints, DNA and other traces that it took police years to identify. He was repeatedly stopped, questioned, arrested and even charged and jailed. One uniformed constable even noted that he seemed likely to be a rapist, but no detective seemed able to join the dots.

He was textbook material for forensic psychology, but when Paul Britton, the profiler working with the police, was asked if one man had killed Ms Nickell and Ms Bissett he dismissed the idea. “It was a completely different scenario,” he said.

The reluctance to investigate Napper for the Nickell murder can be explained only by a belief, shared by the police, the psychologist and Crown Prosecution Service lawyers, that they already had their man. In their view Colin Stagg was guilty, so they ignored the material on Napper.

Robert Clive Napper was born on February 25, 1966, in a hospital in Erith, southeast London, the first son of Brian Napper, a driving instructor, and his wife Pauline. His childhood was spent in a violent home until his mother sued for divorce when he was 10. Her health deteriorated and her children spent periods in foster homes. At 12, Robert was sexually assaulted by a family friend on a camping trip.

As a teenager he was reticent and obsessive, characteristics now thought to be signs of Asperger syndrome.

After school he worked in manual jobs, leaving home aged 21 to live in a bedsit. In November 1989, Pauline Napper phoned Plumstead police station to say that her son was claiming to have raped a woman on Plumstead Common. Police told Mrs Napper that they could not trace the crime. Had they looked a little harder they would have discovered the unsolved case of a 30-year-old woman raped in her home by a masked man who tied her up and put a Stanley knife to her neck. Her children were downstairs.

Psychiatrists who have examined Napper believe that the beginning of his series of attacks coincided with the onset of paranoid schizophrenia. Natalie Pyszora, who supervises his treatment, says that Napper is delusional, believing grandiose things about his life while convinced that he is being persecuted. Napper believes that he has an MA in mathematics, a Nobel prize, medals for fighting in Angola and millions of pounds in a bank in Sidcup. He claims that his family is in Who’s Who, that he could transmit thoughts telepathically and was kneecapped by the IRA.

Professor Don Grubin, a forensic psychiatrist, said that the combination of schizophrenia with Asperger syndrome was a “particularly toxic” mix.

The ferocity of his attacks on women began to build. In March 1992 he attempted two knifepoint rapes then, on a Bank Holiday weekend that May, came an assault that stood out. A woman pushing her two-year-old daughter in her buggy had a rope thrown round her neck and was pulled to the ground, beaten, kicked and raped.

Less than two months later, Ms Nickell was killed. Police in that case drew no link to the Green Chain rapes. Their killer was felt to be someone who knew Wimbledon Common and attention focused on Mr Stagg, a loner who lived nearby.Under the guidance of Mr Britton, an attractive policewoman tried to seduce him into confessing with the promise of sex. Mr Stagg’s eagerness to please Lizzie James, as the officer called herself, led to him being charged in August 1993.

A month after the killing Napper was interviewed over the Green Chain rapes. Police asked him to give a DNA sample but Napper twice failed to keep appointments. Police eliminated him from the inquiry because, at 6ft 2ins, he was taller than the man they thought they were looking for.

In October 1992 Napper was arrested when a search of his flat uncovered firearms, ammunition, knives and a crossbow. He was jailed for eight weeks. Officers did not note the significance of other material in his flat — diaries, hand-drawn maps and a London A-Z on which he had marked dots at points on the Green Chain walk and inside of which was a young woman’s gym membership card. Her address had been circled on the map.

The next April, children playing near Napper’s flat dug up a tin inside which was a Mauser handgun. Napper’s fingerprints were on the tin.

Napper was stopped by police in July 1993 after he was seen peering through the windows of a 24-year-old woman’s flat. He told officers that he was “going for a walk” and was let go. One policeman wrote in his notebook: “Subject strange, abnormal, should be considered as a possible rapist, indecency type suspect.” Instead of stepping up inquiries into Napper, however, police were considering Mr Stagg as a suspect for the Green Chain attacks.

Jim Sturman, QC, then Mr Stagg’s junior defence counsel, recalled: “Colin was going to be pulled out of interview to go off for an ID parade for the Green Chain rapes because he was a close match to the photofit of the man suspected of committing those rapes. But almost as he was on his way the news came back that the DNA wasn’t a match.”

Then, on November 4, 1993, with Mr Stagg in custody, there was an attack with appalling similarities to the Nickell murder. Ms Bissett, a single mother, and her daughter were killed in their flat near Napper’s home.

Ms Bissett’s body was so badly mutilated that it put Mr Britton, the profiler, in mind of Jack the Ripper’s murder of Mary Jane Kelly in 1888. But he remained adamant that despite the similarities between the Nickell and Bissett killings — attractive blonde women stabbed with their young children present — they were not the work of the same man.

Although his bloody finger and palm prints were all over the victims’ flat, Napper was not arrested for the Bissett murders until May 1994.

A search of his home found a footprint made by an adidas Phantom basketball shoe (few of which had been sold in Britain) which matched a bloody mark in Ms Bissett’s kitchen. More than a decade later, forensic scientists discovered that a similar shoeprint had been left at the scene of the Wimbledon Common killing.

A padlocked red toolbox was recovered but a decade would pass before the discovery that paint flecks from

it had been left in Ms Nickell’s son’s hair when Napper flung him to the ground. Inside the box was another A-Z directory with potential attack locations marked.

For four months, from May to September 1994, Napper and Mr Stagg were both in custody. Sources say that there was unease among some prosecutors and police officers who felt the case against Mr Stagg was weak and wanted Napper examined as a suspect for the Nickell murder.

In Wimbledon a lock knife was found buried on the common. In southeast London, it was known that Napper liked to bury his weapons and had bought a knife of the same make.

But the threads were not examined together. The case against Stagg seemed unstoppable until it reached the Old Bailey, where Mr Justice Ognall condemned it as a gross attempt to incriminate. But only yesterday was the file closed on one of Britain’s most horrific murders and one of the most shameful episodes of the Metropolitan Police.

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