Police forces around the country have been asked to scour their unsolved murder records after a man was convicted of killing two women 21 years apart.

Gary Allen, 47, was found guilty on Thursday of killing mother-of-three, Samantha Class in Hull in 1997, and of killing mother-of-four Alena Grlakova in Rotherham in 2018.

Jurors at Sheffield Crown Court convicted him of both killings after a seven-week trial.

He had previously been acquitted of Ms Class’s murder but was re-tried under the double jeopardy laws after he was arrested on suspicion of the murder of Mrs Grlakova two years ago.

Allen, who also served a lengthy prison sentence for attacking two sex workers, had previously told probation workers that he had a pathological hatred of women and enjoyed hurting them.

Police forces around the country have now been asked to examine any unsolved murders, particularly of sex workers, over the past 30-years, amid fears Allen could be a serial killer with many more victims.

Ms Class’s body was discovered by children on the banks of the River Humber in North Ferriby 24 years ago.

Police said the 29-year-old sex worker had been stamped on, strangled with a ligature and run over with a car before her body went in the water.

Nine months later Allen was arrested for drink driving and was charged with murder when a routine DNA swab matched traces on Ms Class’s body.

Credit: Humberside Police

But at his trial he claimed he had paid Ms Class, above,  for sex and insisted she was alive when she left him that night. He was acquitted of murder by a majority decision.

Within six weeks Allen attacked two women in Plymouth, and he was jailed for five years in 2000.

In 2002, he told probation workers of his deep-seated hatred of women and he ended up serving 10 years before being released.

In 2010, he moved to Grimsby where police launched an undercover operation to gather evidence against him in connection with the still unsolved murder of Ms Class.

Allen, who was befriended by one undercover officer, admitted strangling a sex worker and dumping her body in the Humber.

But the confession was not enough to order a retrial and Allen remained a free man.

Mrs Grlakova, below, who was born in Slovakia, disappeared on Boxing Day 2018 and was found naked in a stream in Rotherham in April 2019.

Credit: South West News Service

Following Allen’s arrest, Max Hill, the Director of Public Prosecutions (DPP) personally applied to have the previous acquittal for the killing of Ms Class overturned and he was charged with both murders.

Speaking after the verdict, Ms Class’s daughter, Sophia Class, said her family had been "broken into pieces" by the loss of her "caring, gentle and strong" mother.

In a statement, Ms Grlakova’s husband Viliam Grlak said: "The verdict will not reduce the pain and suffering that we have had to endure since Alena was so cruelly taken from us but it does give us the justice that we hoped to achieve."

Police described Allen as a "despicable, violent man" and a "danger to women".

Mr Justice Goose will sentence Allen next Wednesday.