Gary Allen, 47, killed mother-of-three Samantha Class in Hull in 1997 and mother-of-four Alena Grlakova in Rotherham in 2018.
Allen had been cleared of the murder of Ms Class following a trial in 2000 but this acquittal was overturned in 2019 by the Court of Appeal after a range of new evidence was presented – including the murder of Ms Grlakova.
He was found guilty of murdering both women at Sheffield Crown Court on Thursday (Jun 17) by a jury which deliberated for two days.
Police forces around the UK will now be asked to check on unsolved cases to make sure Allen – who has professed a deep-seated hatred for women, and sex workers in particular – has not committed any further offences.
Ms Class’s body was found by children on the banks of the Humber in North Ferriby 24 years ago.
Prosecutors said she had been “brutally murdered” and a pathologist found she had been stamped on, strangled with a ligature and run over with a car before her body went in the water.
Ms Class, 29, had been a sex worker at the time of her death and left three children – Sophia, Aiden and Lewis.
The jury heard 38-year-old Ms Grlakova’s body was found naked in a stream in Rotherham in April 2019, after she was last seen on Boxing Day 2018.
She was born and brought up in Slovakia and moved to the UK in 2008.
The court was told “Alena was at something of a low point in her life” at the time of her death and had started to work in the sex industry.
But prosecutor Alistair MacDonald QC said “one of the tragic ironies of the case” was that she had been planning to return to live in Slovakia when she was killed.
Allen was cleared of murdering Miss Class following a trial in 2000 but the Director of Public Prosecutions, Max Hill QC, personally applied to the Court of Appeal in 2019 for this acquittal to be quashed arguing that substantial “compelling” new evidence had been gathered.
Just months after the defendant was cleared 21 years ago, he attacked two sex workers separately in Plymouth and was convicted of both assaults.
Following this, in 2002, he was interviewed by probation officers and told them about his dislike of sex workers and women in general.
He told one probation officer: “I like to frighten them. I like to cause pain. I like to make them cry. I like blood. I like to hurt them. I enjoy it. It makes me feel good.”
Mr MacDonald said Humberside Police launched an undercover operation in 2010 to assess the threat posed by Allen.
An officer referred to as “Ian” befriended Allen who told him about an encounter with a sex worker who got angry with him “so I strangled her and dumped her in the Humber”.
Mr MacDonald said: “This was the clearest possible admission to the defendant’s guilt in murdering Samantha Class and disposing of her body afterwards.”
Allen denied killing either of the women and said the confessions he made to “Ian” about killing Ms Class were not true and he was just telling him what he thought he wanted to hear.
Mr Justice Goose will sentence Allen on Wednesday (Jun 23).
The judge told Allen: “You should prepare yourself inevitably for a life sentence, I will determine the details of that next week at 2pm.”