of police ineptitude which scuppered the chances of bringing a beast who raped a pensioner to justice:
After working hard as a secretary for more than 30 years to raise her only son alone and buy a comfortable Victorian terrace house, Hazel Backwell was looking forward to a long and happy retirement.
Comfortably settled in a quiet - and seemingly safe - neighbourhood in Stratford, East London, the 66-year- old spinster enjoyed gardening, listening to radio discussion programmes and sharing a pot of tea with her best friend, who lived a few doors away.
But her contentment was shattered by the sickening ordeal she endured in the early hours of January 23, 1997.
As a BBC documentary will recount this Thursday, it would not only alter the course of her future, but precipitate landmark criminal proceedings with huge implications for British law.
Stirred at 4am by a disturbance in her downstairs bedroom, Hazel awoke to find a burly intruder standing on a chair by the window, his dreadlocks silhouetted in the halflight.
In menacing tones, the man ordered her to roll over and lie face down, whereupon he bound her wrists with flex, beat her with such savagery that he broke a rib and her mouth filled with blood, and raped her.
When the attack was over, he bundled her into a cupboard under the stairs - so small that he had to remove a vacuum cleaner and tool box to squeeze her inside - and barricaded the door with boxes.
He then made off with the few pounds that Hazel had saved to pay a vet's bill, leaving her trapped for 15 hours with the fear that she might die before anyone found her.
It was only when her friend, George Walpole, walked past the house the following evening and saw milk bottles on the doorstep and a light in the basement, where Hazel seldom ventured, that she was freed.
She spent three weeks in hospital, but never really recovered. Unable to face returning to her home, with its terrible memories, she hid from the world in a warden-controlled retirement home, where, five years later, she died.
'The death certificate says my mum died of emphysema but her life finished the day she was raped and locked in that cupboard,' her son David Backwell told me.
'She had been so outgoing and friendly, but from then on she was almost a recluse. She gave away her cat, put on a lot of weight and had a complete nervous breakdown. It's a very sad story.'
It is indeed - and this week, after I discovered how a breathtaking police blunder has ended any possibility that Hazel's attacker might be brought to justice, it took one final, wretched twist.
On the surface, this Thursday's documentary, filmed for the BBC by independent programme maker Mentorn, appears to offer new hope to Mr Backwell and his wife Margaret, who have suffered for 12 years in the knowledge that the rapist is still at large.
In a bold move, the programme makers have secured the right to name publicly the man who almost certainly committed the assault, a chilling character called Wendell Wilberforce Baker who was acquitted on a technicality.
Nine years ago, as the argument about his acquittal exercised Britain's finest legal brains, the Law Lords took the extremely rare step of granting him anonymity - a privilege normally afforded only to rape victims, not defendants.
But now his identity can be revealed because BBC lawyers have persuaded the Lords to overturn the order.
The documentary is thus able to make a compelling argument for Baker, now 52 and living with his girlfriend in a leafy part of East London, to face a retrial following the abolition, four years ago, of the double jeopardy rule, which prevented anyone being prosecuted for the same crime twice.
The programme explores whether DNA evidence, which was deemed inadmissible by the judge at his original trial at the Old Bailey in 1999, could be used at a new hearing, and possibly prove his guilt and concludes 'there could still be justice for Hazel'.
However, I have learned of an astonishing development - one that ends any possibility of a retrial and raises deeply troubling questions about police competence.
So what is the background to this extraordinary and complex case? When Hazel was attacked, her assailant left no fingerprints or other tangible clues.
The only physical evidence detectives could find came from swabs taken from her. These contained the culprit's bodily fluids and were duly run through the National DNA Database, which had been set up two years earlier and was already proving a vital tool in fighting crime. Initially, the computer threw up no matches.
But in January 1998, about a year after the rape, Baker was arrested for another crime - a burglary in Hackney. He gave police an alias but provided a saliva sample from which his DNA could be logged on the database.
A few months later, he was acquitted of this burglary and as the law then stated that the Forensic Science Service could retain only the DNA of people convicted of a recordable offence, it should have been destroyed.
In one of several basic mistakes in this case, however, it was left in the computer's hard-drive, and when another test was run, it showed a clear match with the DNA on swabs taken from Hazel.
According to genetic profiling experts, there was just a one in 17 million chance that the rapist and the cleared burglar - Wendell Baker - were not the same man.
Convinced they had their quarry at last, detectives arrested and charged Baker, then aged 41. He refused to provide a fresh DNA sample, so - as permitted by law - an investigating officer tugged out a fistful of his dreadlocks in the interview room.
This was necessary because only the roots of the hair contain a human's unique genetic code. This second DNA sample also matched that of the rapist.
But (not for the last time) there was a major legal hitch. Because Baker had been rearrested only on the basis of the saliva sample, which should have been destroyed, the defence argued that the genetic match must not go before the jury.
For their part, the prosecution attempted to persuade Old Bailey Judge Alan Hitching that the evidence was so 'clear, compelling and incontrovertible' that he should exercise his discretion and allow it to be heard.
Listening intently to this arcane legal argument from the visitors' gallery, Hazel's only son, David, shared their hopes. Speaking to me last week, the semi-retired security guard, now aged 54, recalled how he sat in court, praying that the man he felt sure had violated his mother's dignity, wrecking her last years, would not cheat justice.
But when the judge ruled in favour of the defence and threw out the DNA evidence, a gloating Wendell Baker walked out of court a free man.
Mr Backwell broke down and wept before delivering the news to his mother. She struggled to comprehend how the sadist who had done such unspeakable things to her could be freed on a mere technicality. 'My mum felt she had been victimised again,' he says grimly.
The bouquet of flowers Hazel received from the Crown Prosecution Service was scant consolation.
The CPS challenged the judge's ruling, but the Appeal Court upheld it. However, the case went to Britain's highest court, the House of Lords, and in December 2000 they ruled that judges could admit DNA evidence - even if it was obtained during an investigation that ended in acquittal.
The following year, prompted in part by this judgment, the then Home Secretary Jack Straw announced controversial plans to retain all genetic samples on the database indefinitely, even when the suspect was cleared.
These developments seemed of little importance to Hazel, of course, because the 800-year-old double jeopardy rule still stood: an individual could not be tried twice for the same crime.
So in 2002, when she was 72 years old, Hazel Backwell went to her grave believing that justice had failed her. Next week's documentary questions why it remains undone.
For, in the aftermath of the Stephen Lawrence case, the double jeopardy law was changed to allow repeat prosecutions where there is 'new and compelling evidence' and the offence is serious enough to be punishable by a life sentence.
Only two cases have subsequently been retried - and it was hoped Wendell Baker might be among the next to come before the courts.
That view was supported by one of Britain's leading authorities on criminal law, University College London Professor Ian Dennis, who opines that the DNA samples taken from Wendell Baker could certainly be classed as 'new' evidence, as they were never placed before the jury at the first trial.
Moreover, given that there is only a one in 17 million possibility that the database match is wrong, it is surely 'compelling'.
So why can Wendell Baker continue to rest secure in the knowledge that he will never again stand trial for the brutal rape of Hazel?
It is because, quite simply, Scotland Yard have made a monumental error. I can reveal that they have lost the file on the Backwell case.
And as it contained vital evidence, including, crucially, the deceased victim's statement, senior officers have privately agreed they would have no chance of persuading the CPS to reopen the Wendell Baker case, let alone of securing a conviction.
'Basically, the case papers don't exist any more,' a shamefaced Scotland Yard spokesman admitted to me. 'Hazel's statement would have been a key part (of the evidence). The file would have been key to any reinvestigation. Therefore, we don't have anything we could consider.
'It is obviously unfortunate that we can't find them (the papers). We have done some extensive searches, including checks to see if there was a copy at the court. There wasn't, unfortunately.'
Unfortunately? That seems a euphemistic way to describe such a serious professional failure.
Losing the file on a case, which, given its far-reaching implications, must surely rate among the more important on the Yard's unsolved crimes list, is scarcely credible.
As Hazel's son, who learned the truth in an apologetic phone call from the Yard several months ago, told me: 'It beggars belief.'
He says he has considered suing the police, but doubts he will do so. For, as he remarks: 'It won't bring back the papers, or my mum. And it's not going to bring this man to justice, is it?'
Given the depraved manner in which he allegedly attacked his mother, Mr Backwell fears it is only a matter of time before Wendell Baker strikes again.
This seems a reasonable assumption. Baker is a recurrent fixture in London's courts and he has convictions for assault occasioning actual bodily harm, damaging property, and carrying a bladed instrument, with several more offences - including threatening to kill - ordered to lie on the file.
His one lengthy jail term appears to have been an 18-month sentence for affray - handed down in May 2001, more than four years after Hazel was raped and battered. He has also garnered a fearsome reputation among his own tough Jamaican-British circle for violence - as has his close family.
His ex-wife, Sandra, by whom he has three daughters (their son died in infancy), was jailed for life in 2005 for hacking a woman to death with a machete and baseball bat in South London.
She and her daughter by a previous relationship were convicted of killing an innocent woman who attempted to intervene when a long-running dispute with two female neighbours erupted.
At all events, viewers of this week's documentary will be left in little doubt about Wendell Baker's true nature.
Venturing outside his semidetached home, a stick in his right hand and a Rottweiler's straining leash in his left, he appears momentarily nonplussed when invited to comment on the case against him.
Then he launches into a foulmouthed and intimidating outburst: 'Go and **** your mother you
****! Get out of my face! **** off!' he snarls, unleashing a flurry of blows that injure the hand of one of the film crew. With that, Wendell Wilberforce Baker stalks off down the street, his simpering female companion in tow.
That this vile man will never face a retrial, even though the law has been changed precisely to prevent his ilk from slipping through the net, is truly a travesty of justice.
Just how much harm might accrue from that lamentably lost police case file, one shudders to imagine.