Chris Dawson's former teenage lover and ex-student, Joanne Curtis, is set to be a key witness in a trial over the murder of his wife Lynette.
Curtis, now aged in her 50s, moved into the former PE teacher's home just two days after the 1982 disappearance of Lynette Dawson and later became his second wife.
Chris Dawson was extradited from the Gold Coast jail about 6.30am today, after being arrested yesterday, and will now face court in Parramatta.
He boarded a Qantas flight shortly before 7am (Queensland local time) this morning, before arriving at Sydney Airport around 9.30am (AEST).
Dawson is expected to be charged with the murder, even though his ex-wife’s body has never been found.
Curtis is believed to have kept a diary as a school student and has been co-operating with homicide detectives, according to The Australian, which produced The Teachers Pet podcast about the unsolved mystery.
Dawson, 70, was taken into police custody yesterday and was denied bail in a Gold Coast court, where he placed his hands over his ears as the magistrate read out the facts of the murder charge he is set to face.
Lyn Joy Dawson, then aged 33, vanished from her home in January, 1982, following the disintegration of her marriage to her husband, whose extra-marital affair with Curtis grew in intensity throughout 1981.
The global success of The Teacher's Pet is being credited with the pushing the police into renewing their investigation, leading to the arrest yesterday.
The podcast has been downloaded 28 million times, with 60 percent of its listeners coming from the US, Great Britain and Canada.
A spokesman for Dawson's family said they were "disappointed" by yesterday’s explosive developments, and claimed there was "clear and uncontested" evidence Lyn was alive long after she disappeared.
NSW police have stated they are comfortable with the strength of the case.
Commissioner Mick Fuller said police, who conducted several digs at the former Dawson family home in Bayview, on Sydney's northern beaches, wanted to find Lyn's body but said that it was "not crucial to finalising the matter".
"We have solved homicides before without identifying the body," Comm. Fuller said.
NSW police had amassed "an enormous amount of evidence.
"There were predominantly statements from witnesses that helped us to pieces of the puzzle is together.”
Following extensive investigations, Strike Force Scriven detectives requested the Office of the Director of Public Prosecutions (ODPP) review their brief of evidence in April 2018.
Earlier this week, the ODPP provided advice to police, and following further inquiries, detectives applied for an arrest warrant before travelling to Queensland.
Comm. Fuller said two additional witness statements had been taken since April, but would not comment on the significance of that evidence.
Mrs Dawson's niece Renee Simms said the family has been waiting for 36 years for some sort of explanation for her aunt's disappearance.
"Absolute relief. My dad was elated," she told the Today show this morning.
Dawson has always maintained his innocence, and claimed his wife had run away to live with a religious cult in remote area of NSW.
In September a team of NSW police spent several days digging areas around the former Dawson family home, including by a swimming pool, where police believed it was possible Ms Dawson had been buried.
But they found no human remains or other evidence on the property, which is surrounded by bushland.
© Nine Digital Pty Ltd 2018