It was just two minutes long and contained 257 words, but it sent the biggest police manhunt in British history on an 18-month wild goose chase. Nick Morrison looks at how Wearside Jack hindered the search for the Yorkshire Ripper.

TO George Oldfield, it was the glimmer of hope he desperately needed. After four years, the hunt for the Yorkshire Ripper seemed to be getting nowhere. Ten women had been killed, eight in West Yorkshire, two in Manchester. Fear was widespread. Women dared not venture into the night alone. The pressure for an arrest became insufferable.

Mr Oldfield, Assistant Chief Constable of West Yorkshire Police, had been appointed to lead the investigation after the fifth murder. The first four victims had been prostitutes, but when 16-year-old shop assistant Jayne MacDonald was killed, perhaps mistaken for a street girl after she was spotted talking to two girls on a street corner, the case came to national prominence.

The realisation that a serial killer was on the loose terrified entire cities and shocked the country. The killer was dubbed the Yorkshire Ripper by a Press which both reflected and fuelled the hysteria. Mr Oldfield set up a Ripper Squad and was given vast amounts of officers and resources.

But by the summer of 1979 it was clear that police were no nearer catching the Ripper than they had been when he claimed his first victim almost four years earlier. Thousands of suspects had been interviewed, hundreds of lines of inquiry pursued, no-one had been arrested. The clamour for progress became deafening.

Then, on June 17, a package was posted to Mr Oldfield. Marked, "From Jack the Ripper", it contained a tape. It was a taunting declaration of the police failure, and a warning that the killer would strike again.

"I'm Jack. I see you are still having no luck catching me," the voice on the tape said. "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 voice on the tape appeared to have inside knowledge of the killings and spoke of another unsolved murder, in Preston. Mr Oldfield believed it was the start he needed. He had already received two letters, posted in Sunderland, with a third sent to the Daily Mirror offices in Manchester.

The voice on the tape had a distinctive North-East accent. Experts narrowed it down to the Castletown area of Sunderland. Mr Oldfield was convinced the author of the letters was the man who made the tape, and that man was the killer. It was to prove a disastrous mistake. On June 26, the tape was broadcast nationally. Dial-a-Ripper phonelines were set up where callers could ring in and listen to the tape.

Overnight, the investigation switched from West Yorkshire to Wearside. Thousands of men in Castletown were interviewed and asked to provide swabs for analysis. Anyone without a Wearside accent was discounted from the inquiry. One of those, in July 1979, was Peter Sutcliffe. The interviewing detectives were suspicious, but Sutcliffe's handwriting and voice did not match the tape, and their report was filed as a low priority.

But the hunt for a Sunderland killer proved as fruitless as the earlier search. Despite numerous tip-offs about various suspects for the man on the tape, detectives were unable to find someone whose accent matched and could be put at the scene of any of the crimes.

And the killings continued. In September 1979, three months after the tape had been broadcast, Barbara Leach was murdered in Bradford. The following year, the Ripper claimed two more victims: Marguerite Walls and Middlesbrough girl Jacqueline Hill, who was studying in Leeds at the time.

In November 1980, Mr Oldfield was replaced as head of the investigation by Detective Chief Superintendent James Hobson. Mr Oldfield had suffered a heart attack the previous year and was eventually forced to retire. He had staked his career on the Wearside link, and he had lost.

Det Ch Supt Hobson downplayed the importance of the tape and the letters, without discarding them altogether. But when the breakthrough came, it was more a fluke than inspired police work.

By January 1981, a quarter of a million names had been filed on individual cards. More than 30,000 statements had been taken. None of this led to Sutcliffe's arrest.

But on the night of January 3, a police car drew up behind a brown Rover containing 24-year-old prostitute Olivia Reivers and her client. Suspicious at their behaviour, the officers checked the number plate and found it belonged to a Skoda.

They arrested the pair and took them to the station, but one of the officers was suspicious. Sergeant Robert Ring decided to return to the scene, and behind a nearby storage tank he found a hammer and a knife. He reported the find to the Ripper Squad.

Interviewed by Detective Inspector John Boyle, Peter Sutcliffe quickly confessed he was the Ripper. "Well, it's me. I'm glad it's all over," he said. It was only then that police admitted the killer did not have a Wearside accent.

Just five months later, in May 1981, Sutcliffe was jailed for life after he was convicted of the murder of 13 women and the attempted murder of seven more. He was sent to Parkhurst Prison on the Isle of Wight, but later transferred to Broadmoor mental hospital in Berkshire, after he was diagnosed with paranoid schizophrenia.

The hoaxer, Wearside Jack, shifted the investigation away from Sutcliffe for 18 months. As well as costing around £4m, the diversion has also been blamed for the deaths of the Ripper's last three victims, killed while police were looking elsewhere.

But it is far from certain that those lives would have been saved without the tape, and without Mr Oldfield gambling everything on its authenticity. By June 1979, Sutcliffe had already been interviewed four times. A £5 note found in the handbag of one of his victims had been traced back to his employers, but police accepted Sutcliffe's alibi.

After Sutcliffe's conviction, the investigation into the identity of Wearside Jack was scaled down. Perhaps to hide their own embarrassment at being so thoroughly duped, perhaps out of consideration for Mr Oldfield, whose career had been blighted by his mistake, police seemed reluctant to pursue the hoaxer.

But theories about his identity persisted. Was he an accomplice who had been involved in the killings? A police officer, with a grudge against Mr Oldfield? Was he acting alone, using newspaper reports to provide apparently inside information? A killer who committed the Preston murder but wanted to shift the blame onto the Ripper?

Until the arrest on Tuesday night, little had been heard recently of the police's attempts to catch Wearside Jack. It remains to be seen whether one of the most enduring mysteries of the Yorkshire Ripper's reign of fear is now any closer to resolution.

The Ripper and the Hoaxer

Summer 1975: Peter Sutcliffe began attacking women, two in Keighley and one in Halifax. All three survived but police did not link the attacks.

October 1975: Sutcliffe attacked and killed Wilma McCann, a 28-year-old prostitute, in Leeds, battering her with a hammer then stabbing in her the neck, chest and abdomen.

January 1976: Emily Jackson, 42, from Leeds, was battered with a hammer and stabbed 52 times with a screwdriver.

February 1977: Leeds prostitute Irene Richardson, 28, killed.

April 1977: Sutcliffe strikes for the first time in his home town, killing Patricia Atkinson, 32, in Bradford.

June 1977: The killings gain national attention with the murder of 16-year-old shop assistant Jayne MacDonald in Leeds.

October 1977: Sutcliffe chooses Manchester for his next attack, killing 20-year-old Jean Jordan. Sutcliffe tries to cut off her head.

January-May 1978: Three women killed in four months - Yvonne Pearson, 21, in Bradford, Helen Rytka, 18, in Huddersfield and Vera Millward, 40, in Manchester.

March 1978: First letter sent to Assistant Chief Constable George Oldfield, in charge of the investigation. Posted in Sunderland, it warns: "Warn whores to keep off streets cause I feel it coming on again." Three days later, a second letter arrives at the Daily Mirror offices.

March 1979: Third letter sent to Mr Oldfield, taunting police for their failure to stop him.

April 1979: Building society clerk Josephine Whitaker, 19, killed in Halifax.

June 1979: Tape posted to Mr Oldfield, again taunting police for their failure to catch him. Mr Oldfield makes the tape public and the hunt for the killer switches to Wearside.

September 1979: Barbara Leach, 20, killed in Bradford.

August 1980: Marguerite Walls, 47, killed in Leeds.

November 1980: Jacqueline Hill, 20, becomes Sutcliffe's 13th and last victim, when she is killed in Leeds.