image copyrightHumberside Policeimage captionGary Allen was convicted in 2000 for attacking two sex workers in Plymouth, months after he was acquitted for the murder of Samantha Class

'A dangerous and violent man', Gary Allen walked free from court 20 years ago when jurors cleared him of murder. But police, reporters and victims who survived his wrath never doubted his guilt. It would take two decades of investigations, a change in the law and the testimony of a woman who fought for her life when the two came face to face to finally cage the killer who nearly got away with murder.

It was a typical working night for 24-year-old Melanie (not her real name) in April 2000.

She'd just been approached by a man "lingering around, looking for business" yards away from the hubbub of Union Street in Plymouth's Stonehouse Street area – notorious for red-light activity at the time.

The customer sported a lengthy blue coat, jeans, white trainers and long, swept-back hair with "a bit of stubble" on his face. They agreed a price and walked to a quiet part of the street, holding hands as they passed a police van so they'd look like a couple.

When Melanie asked to be paid upfront, the man's demeanour "switched" and he grabbed her by the neck. "He was calling me awful names… it was just rage. He obviously wanted to hurt me bad and I don't even know why," she says.

"He got me in a headlock and dragged me back and I fell on to the floor. Then he was just punching me in the back of my head. He tried to put his whole fist in my mouth so I bit him. He still carried on hitting me and I was just screaming – 'Someone help! Someone help me!' – screaming and screaming."

The noise drew the attention of a nearby policeman. Spooked, the attacker ran away and pushed an officer to the floor before he was caught. Had it not been for the man in blue, Melanie, now 45, believes she would not be alive today.

"I don't know where I got the strength from that night but I was fighting for my life. I knew if I didn't get away, I was going to be killed," she says.

Melanie's assailant was charged and sentenced to five years in prison for attacking her and another sex worker. The day she gave evidence at Plymouth Crown Court, Melanie was shocked to learn from a police contact about the man's dark secret – a murder charge from which he had walked free.

His name was Gary Allen.

Melanie was not his first victim and, sadly, would not be his last.

Almost three years earlier, on the morning of 26 October 1997, schoolgirl Jennifer Harvey went for a walk with her friends along the riverbank in North Ferriby, East Yorkshire. They had just returned a film to the local video shop after their sleepover the night before.

Their stroll along the gravel path came to a halt when they spotted a body, naked from the waist and face-down in the muddy bank about 10m (33ft) from the shore. It belonged to 29-year-old Samantha Class, a mother of three young children. In her statement to police, Jennifer said she could see blonde hair, as well as bruises and marks on the body.

Ms Class' injuries showed she had been stamped on, strangled with a ligature and run over by a car before her body was dragged to the water. The grim discovery would start a Humberside Police investigation which would continue on and off for nearly two decades.

image copyrightHumberside Policeimage captionSamantha Class's body was found in 1997 by three schoolchildren in North Ferriby, East Yorkshire

Former detective Ken Bates, who led the first investigation into Ms Class's murder, recalls recovering her body and items of her clothing scattered among the rocks. He remembers being shocked by her "absolutely awful injuries".

Media appeals followed, including a spot on Crimewatch and a £5,000 reward offered for information. After nine months, Gary Allen was arrested for drink-driving in the early hours of 6 July 1998. A routine DNA swab matched traces of semen found inside Ms Class's body. The link was enough for police to launch a surveillance operation which ended in Allen's arrest for Ms Class's murder.

As the original trial in February 2000 approached, Mr Bates and his team believed they had significant evidence against Allen and were "very confident" jurors would find him guilty. They had "left no stone unturned" and were in no doubt they had the right man.

From the dock at Sheffield Crown Court, Allen said he had driven to Hull's red light district on 25 October 1997, where he paid Ms Class £30 for sex. He said she became "angry" after a condom split, the pair rowed, and he last saw her, alive, walking away from his car. Prosecutors asked why he had scrapped his vehicle days later. Jurors were also told how he had washed his clothes in the early hours of the morning soon after the killing.

In the end, they found him not guilty by a majority decision.

"I was sorely disappointed," says Mr Bates, "personally shocked". "I know the investigation team was. Even the faces of his defence team were shocked".

image captionFormer detective Ken Bates worked on the original inquiry into Samantha Class's murder until his retirement in 2000

Mr Bates retired months later. The case would be the last of his career and one that left some "deep regret".

"I was disappointed for not only failing to get justice for Samantha but also failing to get justice and the comfort of justice, closure, for her family," he says. "But the main reason I was disappointed was that I knew that Gary Allen would go on to reoffend.

"He's a dangerous violent man and he wasn't going to stop."

After his acquittal, Allen would prove the detective right.

On the day he walked out of court a free man, Allen was given some money and dropped off at Sheffield train station. He was told to "get as far away from Yorkshire as possible", recalls former Hull Daily Mail crime reporter Lisa Welton.

Ms Welton, who then went under the name of Lisa Berry, covered the original trial for the newspaper. She was behind an exclusive story, published the day after his acquittal, based on a leaked social services report which revealed Allen's history of violence.

The article revealed Allen was referred to a child psychiatrist at the age of eight for aggressive behaviour towards his younger siblings. At 14, he attacked his mother with an iron bar while she was recovering from an operation. In another attack which bore chilling hallmarks of his subsequent assaults he grabbed a schoolgirl by the throat and hit her on the head.

"That particular evidence never came out in court, it couldn't happen," Ms Welton says. "But we did run the story that this Gary Allen had got off, he was the person responsible and had a history of violence against women."

image copyrightHull Daily Mailimage captionAn article by the Hull Daily Mail in 2000 revealed Allen had a history of violence going back to his childhood

Within six weeks of walking free, Allen moved to Plymouth where he attacked Melanie and the other woman. Both suffered similar patterns of violence, with Allen squeezing their throats and punching their heads.

Soon after Allen had re-offended, Ms Welton received a call from a police contact informing her about the attacks.

"I think there was a sense of shock but also that sense of it could've been stopped," she says. "It's almost that we did have the right man and he got away with it."

The Plymouth assaults left a trail of fear among those working in the sex industry and, after he had served his jail term, warnings about Allen were posted on websites used by escorts and sex workers. Melanie says women she worked with were "petrified" once news of Allen's acquittal for murder spread.

For Melanie, the after-effects of her harrowing ordeal were made worse by knowing she may have narrowly escaped murder herself. Within 12 months she had quit the sex industry because she no longer felt safe. Her drug habit had spiralled out of control and she turned to shoplifting. Melanie suffered nightmares and flashbacks and, wherever she went, would see Allen's face "all the time, following me, going to kill me". On one occasion, she had to phone the police when she mistook another man for her attacker.

Allen, meanwhile, served almost 10 years in prison, adding extra time for various breaches, including the removal of an electronic tag and going on the run in 2004 after his release on licence. He moved to Grimsby in 2010, and Humberside Police launched a year-long undercover probe named Operation Misty in a bid to gather more evidence on Ms Class's murder. Double jeopardy laws in the UK had been scrapped in 2003, meaning Allen's acquittal could be quashed and a retrial ordered if compelling new evidence was found.

media captionA recording of Gary Allen's confession to Samantha Class's killing was released after his second murder trial

A group of seven undercover officers posing as shady criminal underworld characters befriended Allen, using cover stories and techniques such as staging illicit deliveries and burning bloodied clothes to gain his trust. It paid off, and among 400 hours of secret recordings came the breakthrough the force had been waiting for: a confession to Ms Class's murder.

During the conversation, captured in February 2011 by an undercover officer known as Ian, Allen openly admits to strangling a sex worker who he then "dumped in the Humber". "That's just the way I was then," he casually adds.

But the recorded admissions alone would not be considered "compelling evidence" to convince a Court of Appeal to overturn the original verdict and grant a retrial, says Director of Public Prosecutions (DPP) Max Hill.

  • How the law caught up with Gary Allen

"In many of the early cases, it was an advance in scientific evidence, that was the hallmark of a double jeopardy case. This is not one of those cases," he says. "And so even with the undercover evidence confessions, it was necessary to put around that more evidence to satisfy the tests of new and compelling evidence".

Tragically, the evidence needed to secure a retrial came eight years later when Alena Grlakova's body was found in a stream in Rotherham in April 2019, nearly four months after she had disappeared.

The mother-of-four, from Slovakia, moved to the UK in 2008 with her husband. Their children were aged between 12 and 19 at the time of her death. After separating from them in 2013, she developed a drug habit and became a sex worker. Three years later, she met Allen in the Parkgate area of Rotherham, where he had moved in 2012 following further stints in prison for breaching a Sexual Offences Prevention Order (SOPO). They developed a friendship and she regularly visited his home on Bradbury's Close.

A month after Ms Grlakova was reported missing by her husband, Allen was back in custody for further breaches of the order and, following his arrest on 26th January 2018, South Yorkshire Police found a number of gadgets during a search of his property, including a mobile phone found to contain a series of images of women found dead in a similar way to Ms Grlakova. Officers also recovered audio recordings he had made of his conversations with the 38-year-old, in which he could be heard shouting "get out or I'm going to chuck you out".

media captionRecordings made by Gary Allen captured him making threats towards Alena Grlakova days before her murder

Allen's neighbours Linda and Tony Leech allowed police to access CCTV footage taken from their property which showed Ms Grlakova going in and out of the killer's home.

The Leechs could not recall seeing her, but they remember Allen as a man who they "hardly ever saw and had kept to himself".

A few days after the police visited to review their CCTV, Mr Leech says, the drains became blocked at their home and some neighbouring properties. When it was cleared the cause turned out to be a football-sized ball of wet wipes. Police told the couple it was from Allen's flat "where he'd been wiping, wiping everything down," Mr Leech says.

Armed with enough evidence to charge him with Ms Grlakova's murder, prosecutors also applied to overturn Allen's original acquittal for Samantha Class's killing. They were granted a retrial.

image captionNeighbours Linda and Tony Leech said they were "shocked" to discover a killer was on their doorstep

Part-way through the seven-week trial, Melanie had an unexpected visit from Humberside Police. After answering her door to the officers, she was landed with another bombshell. This time it was the news that her attacker was on trial for two murders.

"I couldn't believe it. I just collapsed. I just burst into tears. I was in shock. It still feels strange, it feels like a dream really. Still doesn't feel real to me," she says.

After talking it through with her partner, Melanie decided she would make the seven-hour journey from Plymouth to Sheffield to give evidence in the trial. Entering the witness box for a second time "brought it all back", she says, and she was left struggling once again. She recalls being "a bag of nerves" as she prepared to testify. She remembered the "awful" experience of testifying 20 years ago, faced with a "smug" Allen who appeared confident he would walk out of court once again.

During the latest trial at Sheffield Crown Court, Allen maintained his arrogant demeanour, abruptly telling the prosecutor to "stop with the commentary and just ask me the questions" during cross-examination. In another round of questioning he dismissed queries about internet searches from years past as "ridiculous", and during another told barristers: "He's your witness so you go fetch him". He maintained the murder charges and retrial were part of a 20-year conspiracy to "fit him up" involving lying probation officers and other agents.

Thankfully, Melanie says, she was spared from Allen's bravado when he refused to enter the courtroom during her testimony, but the experience still left her "a nervous wreck". "I think it was more the fear of seeing him," she says. "I built myself up to face him".

image copyrightHumberside Policeimage captionSamantha Class's boot was found discarded among the rocks on the shore of the River Humber

Despite the "bad memories and flashbacks", Melanie says her decision to give evidence a second time was fuelled by the need to get closure and the hope of putting the killer behind bars once and for all to protect other women. She believes Allen will have attacked more who have not come forward for fear of revealing their work in the sex industry.

"I just thought: 'How the hell could he have got away with murder?' I don't get it," she says.

"If he got put away the first time then I wouldn't have been attacked and this other lady wouldn't be dead.

"I wanted to do this because if there is anybody out there that he has attacked, they need to come forward because he needs to never get out again. They need to save other women."

After 20 years and two trials, the quest to bring a killer to justice has finally been completed. And while the force's investigation team can breathe a sigh of relief, the case files remain open as detectives follow potential leads about further victims, with South Yorkshire Police saying its investigation into Gary Allen is far from over.

Det Ch Insp Mark Oughton, who led the force's inquiry into Ms Grlakova's murder, says officers have traced Allen's movements and former addresses, liaising with the National Crime Agency's analytical section and accessing its record of all unsolved murders and serious sex attacks.

"What we'll be doing is writing to a number of forces to ask them to look at those crimes in those areas, for them to consider whether Gary Allen may be responsible for the crimes in their area," he says.

image copyrightSouth Yorkshire Policeimage captionThis CCTV image, taken from the Traveller's Inn pub in Rotherham, captured Ms Grlakova's last known movements

While the prospect of Allen spending his remaining life behind bars comes as "a relief", Melanie says she is yet to feel completely liberated from the pain he inflicted on her more than two decades ago.

"But I'm in a different place now. I've had a little girl who's 11. I've been clean off drugs for nearly 13 years," she says.

Despite turning her "chaotic" life around, she continues to rely on medication to tackle her sleeplessness, anxiety and depression and regularly attends therapy sessions.

"I was suffering with this all this time and now I'm going through it again even more so. It's like its pushed me back.

"I was trying to move on from it, even 20 years on, and now it's like everything's back. So it's like I've got to start again now to try get him out of my head.

"This will never ever leave me until I die. Ever."