IT was June 26, 1979, when a recorded message lasting two minutes and containing 257 words was played to the world. The head of the Ripper Squad, George Oldfield, was convinced the taunting tape was the work of the serial killer he had been hunting for the past four years.

The Yorkshire Ripper, as he would become known, had first struck in Leeds in October 1975, and had gone on to butcher at least a further nine women and attempt to kill seven more.

It was the biggest manhunt the country had ever seen and Assistant Chief Constable Oldfield now had a firm focus for his inquiry - the Castletown area of Sunderland.

Voice experts had told the experienced officer that the man who made the tape was from the former mining community and spoke with a pronounced lisp.

But Oldfield's decision to switch the investigation from the Ripper's stalking ground of West Yorkshire to Wearside proved to be one of the biggest errors in British criminal history.

Almost overnight, the hunt shifted to the North-East and anyone who did not have a Sunderland accent was eliminated from the long-running and expensive inquiry. Peter Sutcliffe - who was eventually arrested and jailed for life for the killings - had been interviewed on nine occasions, but ruled out as a suspect on some occasions because of his Bradford dialect.

In the 18 months between the tape being broadcast and Sutcliffe finally being caught in January 1981, he went on to murder a further three women while police concentrated their efforts on the North-East.

At his Old Bailey trial, Sutcliffe said the hoax letters and tape had acted as a "diversion" which allowed him to carry on what he called his "mission" - to kill women.

"It served to take a great deal of the investigation elsewhere," the multiple-killer said.

Sutcliffe pleaded not guilty to 13 counts of murder, but guilty to manslaughter on the grounds of diminished responsibility because he said he was working on behalf of God to rid the streets of prostitutes.

Trial judge, Mr Justice Boreham, ordered that the not-guilty pleas should not be accepted, and following a two-week trial, Sutcliffe was found guilty and sentenced to life with a minimum recommendation of 30 years.

A subsequent appeal was denied, and he has since been told he will never be released, and will die a prisoner.

Mr Justice Boreham said at the end of the trial: "The scent was falsified by a cynical, almost inhuman, hoaxer. I refer to the tape and letters. I express the hope that one day he may be exposed."

Oldfield's hunt for the Ripper was over and the killing spree was at an end, but the hoaxer who helped Sutcliffe remain at large and a threat to women had still not been found.

Wearside Jack had not just sent the tape, but also a series of letters, which also taunted the police for failing to catch the serial killer.

The tape had been sent to Oldfield on June 17, 1979, and was marked "From Jack the Ripper".

It said: "I'm Jack. I see you are still having no luck catching me. I have the greatest respect for you, George, but Lord! You are no nearer catching me now than four years ago when I started.

"I reckon your boys are letting you down, George.

"They can't be much good, can they? The only time they came near catching me was a few months back in Chapeltown when I was disturbed. Even then it was a uniformed copper, not a detective.

"I warned you in March that I'd strike again. Sorry it wasn't in Bradford. I did promise you that, but I could not get there.

"I'm not quite sure when I will strike again, but it will definitely be some time this year, maybe September, October, even sooner if I get the chance.

"I am not sure where, maybe Manchester. I like it there. There's plenty of them knocking about. They never learn, do they George? I bet you've warned them but they never listen."

The first letter was sent to Oldfield from Sunderland in March 1978 which said: "You probably look for me in Sunderland, don't bother.

"I am not daft. Just posted letter there on one of my trips. Not a bad place compared with Chapeltown."

A second letter was sent three days later to the offices of The Daily Mirror, in Manchester, part of which read: "I have already written to the chief constable (sic) George Oldfield 'a man I respect' concerning the recent Ripper murders. I told him and I'm telling you to warn them whores I'll strike again and soon when the heat cools off."

Neither letter was made public at the time because they were thought to be the work of a crank, but police opinion changed when a third letter and the tape arrived.

They contained information which officers believed would be known only to someone with a detailed knowledge of the killings - Wearside Jack and the Yorkshire Ripper had to be one and the same, they concluded.

An increasingly-desperate Oldfield played the recording to a packed Press conference and in doing so gambled his entire career on the authenticity of the letters and tapes.

He set up Dial-the-Ripper phone lines where the public could ring and listen to the tape, and devoted a huge proportion of his officers to the task of identifying Wearside Jack.

It was drilled into detectives that they could discount suspects if their accents did not match that of the softly-spoken voice heard lisping on the tape.

In July 1979, Sutcliffe was interviewed for the fifth time - by Detective Constables Andrew Laptew and Graham Greenwood - but their report was simply marked "to file" because the voice and handwriting did not fit the bill.

Two months later, the Ripper struck again, in Bradford, and 20-year-old student Barbara Leach became his tenth victim.

Once again, the murder of a woman who was not a prostitute aroused the public and prompted an expensive publicity campaign, which wrongly also pushed the Wearside connection.

In April 1980, Sutcliffe was arrested for drink-driving, but while awaiting his trial, killed two more people in Leeds - Marguerite Walls, 47, in August, and Middlesbrough student Jacqueline Hill, 20, in November.

Following Jacqueline's murder, one of Sutcliffe's friends reported him to the police as a suspect, but the information vanished into the vast cabinets of evidence already created.

He also attacked two other women who survived - Upadhya Bandara, 34, in Leeds, and Theresa Sykes, 16, in Huddersfield - before he was finally caught in January 1981.

Sutcliffe was stopped by police in Sheffield while in a car with prostitute Olivia Reivers, 24, and the pair were arrested.

Having found his car to have been fitted with false number plates and because he matched so many of the characteristics of the Ripper, Sutcliffe was questioned while police searched his house.

Detectives also went back to the scene of his arrest and found a hammer, knife and rope he had disposed of when he asked officers if he could urinate before they took him in.

When he was finally snared, he told police: "Well, it's me. I'm glad it's all over. I would have killed that girl in Sheffield if I hadn't been caught.

"But I want to tell my wife myself. It is her I'm thinking about - and my family. I am not bothered about myself."

During the next 15 hours, Sutcliffe gave a detailed statement about his life as the Ripper.

The Yorkshire Ripper was jailed for life in May 1981 for the murder of 13 women, but Wearside Jack remained at large.

In the intervening years, a host of theories were proffered - including the hoaxer being a former police officer - but the investigation was never given a high priority.

Only last summer, the hunt for Wearside Jack was dealt a blow when West Yorkshire Police revealed they had lost the letters.

But in September, during a cold-case review, a DNA match was found between some samples that had been kept from the time and an entry on the police national data-base for a man from Sunderland arrested for being drunk and disorderly in 2001.

The following month, police swooped on an ordinary-looking house on the Ford estate in Sunderland and arrested John Humble, a 49-year-old jobless labourer.

The dramatic development was the beginning of the end of one of the great unsolved mysteries of British criminal history.