A 49-year-old man was arrested at his home in the Sunderland area yesterday as part of inquiries dating back more than a quarter of a century.
Detectives brought the man to West Yorkshire last night for questioning on suspicion of attempting to pervert the course of justice.
A tape of a man with a chilling Wearside accent was sent in 1978 and 1979 and were directly addressed to Assistant Chief Constable George Oldfield who was leading the hunt for the Ripper. They began with the words: "I'm Jack. I see you're still having no luck catching me..."
The messages – linked to letters also sent to Mr Oldfield, who died in 1985 – were described as probably the most important clue to the killer's identity by police who had spent four years investigating 10 murders and other vicious assaults on women across the North, without success.
They caused a huge diversion in the investigation, which eventually led to the arrest and conviction of Peter Sutcliffe, wasting many vital months of police time and costing an estimated £4m.
Last night a West Yorkshire Police spokesman said in a short statement: "Officers from West Yorkshire this afternoon travelled to the Sunderland area where they arrested a 49-year-old local man on suspicion of attempting to pervert the course of justice.
"This relates to the hoax letters and tape that were sent to police during the Yorkshire Ripper murder investigation."
He said the man was being brought to a police station in West Yorkshire but refused to release any further details.
The tape of a man dubbed "Wearside Jack" was made public in June 1979, and his taunting tones became familiar across the country.
The man threatened to kill again in Manchester, and said he would kill himself if police got too close. He boasted about how police had failed to capture the killer.
A huge publicity campaign was launched, in the belief the man was the Ripper, urging people to study handwriting in the letters and to listen to the tape on a special telephone number.
Hundreds of people claimed they could identify the voice of the killer.
The hoax took investigations away from the suburbs of Bradford, where quietly-spoken Yorkshireman Peter Sutcliffe, who had already killed 10 times, was living. At one point police suspicions about Sutcliffe were raised, but he was released because he did not have a Wearside accent.
He went on to murder more victims in the Leeds area, including Barbara Leach, 20, a Bradford University student from Kettering; Margo Walls, 47, a civil servant from Farsley, Leeds; and Jacqueline Hill, 20, a Leeds University student from Middlesbrough.
Police took the tape to working men's clubs all over the North, and played them in every prison.
Detectives were convinced the voice was that of the Ripper because of key facts on the tapes which they mistakenly felt only the murderer could know.
Their belief was backed by psychiatrists who studied the tape, and by handwriting experts.
It was not until Sutcliffe was arrested, almost by accident, in January 1981 in Sheffield, that they knew for certain the tape was a hoax.
Police have concentrated their efforts to find the hoaxer in the Sunderland area after being guided by experts in dialect who said it was peculiar to the Castletown area of the town.
Allegations that a policeman made the hoax tape in frustration at the investigation have been among those examined by detectives. And earlier this year police admitted the original tape and letters had been lost and a hunt was underway to find them again.
Last night Michael Bilton, author of Wicked Beyond Belief, one of the most recent books about Peter Sutcliffe, described the arrest as "quite extraordinary," and said the latest arrest could have been the result of a number of scenarios.
"I can only imagine someone or thing has exposed this man, either from his fingerprints or some other evidence. It could be that this was some sort of death-bed confession by someone else who knew what had happened.
"The DNA evidence in the case was supposed to have been disposed of, so it may be that they have got some of it back again." When asked whether the Ripper may have been working in tandem with an individual in Sunderland, Mr Bilton said: "This has been suggested a number of times. There was a cafe owner in Sunderland who said that Sutcliffe used to go there with a man and that they were very close.
"She believed that Sutcliffe was involved with this man and probably got him to send the tape. Sutcliffe subsequently denied that and there has never been any evidence to draw the link.
"Police called in experts from Leeds university who were able, using their knowledge of dialect, to pinpoint a small area of Sunderland where this man was from.
"It is almost inconceivable that the man was not screened or got through the screening process.
"He could have got someone to have written down the letter for him. He could have been living in some other place, but it looks like the person escaped through the very thorough screening process."
mike.waites@ypn.co.uk