Wearside Jack documentary: What to expect from The Yorkshire Ripper Files episode on Sunderland hoaxer John Humble

The Yorkshire Ripper Files: A Very British Crime Story is a three-part series looking at the crimes of infamous serial killer Peter Sutcliffe, the police investigation, and the impact his killings and attacks had on survivors and their families.

The series began last night at 9pm on BBC Four, and continues at 9pm tonight with an episode focusing on Wearside Jack.

Last night's series looked at the attacks and investigation up until 1979, including interviews with survivors, victims' families, police and others involved in the case.

Director Liza Williams also explored the difference between the way the women were characterised by the investigation and how they are remembered by those who knew and loved them,.

She looked at how victims were listed as being of "loose morals" and how eyewitness evidence was overlooked from survivors who didn't fit the police's victim profile.

Tonight's episode will look how John Humble's hoax letters and tape diverted the police investigation - which became known as the "Wearside Jack" case.

The BBC blurb reads: "Following the murder of Josephine Whitaker in April 1979, Peter Sutcliffe’s crimes started to make headlines across the country and the investigation became consumed by a series of letters and a tape that claimed to come from the killer himself.

"The letters and tape, addressed directly to George Oldfield, West Yorkshire’s (assistant) chief constable, were sent by a man calling himself Jack the Ripper.

"Oldfield was so certain that they came from the killer that other suspects were ruled out on the basis of their handwriting or whether they had a north-east accent like the one on the tape."

In tonight's episode, Williams will look at how Oldfield’s character and his hunches impacted on the direction of the investigation and what evidence was ruled in or out.

The BBC said interviews with survivors and relatives of those who were attacked will recount in tonight's how they were not listened to when their descriptions of the attacker did not match the voice on the tape.

Williams also speaks to police officers who tell her about other promising lines of inquiry, tracing clues left behind at murder scenes, which were sidelined when the ‘Wearside Jack’ evidence took centre stage.

Trailer clips at the end of last night's episode featured colour footage of officers listening to the chilling tape.

Tonight's episode will also look at how the Yorkshire Ripper case impacted on wider society at the time.

"Terror grew and the killer started to become a kind of cult figure, with Yorkshire Ripper chants at football matches and Thin Lizzy’s Killer on the Loose topping the charts," the BBC blurb reads.

Williams looks at how this "myth-making" provoked anger from women and the police’s failure to catch the killer led to a demonstration on the streets of Leeds.

The episode ends with the arrest of Peter Sutcliffe, revealing how his name was already in multiple police files.

The blurb reads: "He had been interviewed nine times during the course of the investigation.

"He did not have a Wearside accent like the voice on the tape, but was born and bred in Yorkshire. Had the police arrested him the first time he was questioned in November 1977, seven women’s lives might have been saved."