But it is feared the number of victims could run into hundreds, as the vast majority of men he targeted were unaware they had been attacked. When contacted by police, none of the victims wanted to know the details of what happened to them and two went on to attempt suicide. Loading Replay Replay video Play video Play video Sinaga, who moved to Britain in 2007, operated out of his Manchester flat, which was just metres from many of the city's popular nightclubs and bars. Leaving the apartment late at night, he would prey on those who looked drunk or vulnerable. After striking up conversation, he would lure them back to his flat with offers of drinks or the opportunity to charge their phones.

Sinaga would then spike their drinks with the class-C party drug GHB. He would rape or sexually assault them, often numerous times, filming the attacks on his phone. His youngest victim was 17 and the oldest 36. The true scale of Sinaga's offending may never be known. Police have established that at least 195 men were attacked and filmed, but more than 70 are yet to be identified. All but three of the 48 men who could be identified were heterosexual. For two and a half years, barely a week went by when he did not carry out an attack, sometimes raping two different victims in the same weekend. He was eventually caught in June 2017 when his final victim regained consciousness during the rape and managed to fight Sinaga off before reporting him to the police.

Loading When officers examined Sinaga's mobile phone and other digital devices they found a hoard of horrendous footage showing him raping his victims. He often took "trophies" from those he attacked, stealing mobile phones, watches and other keepsakes. Detectives traced many victims because Sinaga looked them up on social media after the assaults, sometimes boasting to friends about the liaisons. Sinaga only gave evidence in two of the four trials and claimed all of the sex had been consensual, despite the fact some of his victims could be heard snoring in the footage.

Sentencing him to life with a minimum term of 30 years, Judge Suzanne Goddard QC told Sinaga: "You are an evil serial sexual predator who has preyed upon young men that came into the city centre wanting nothing more than a good night out with their friends. "One of your victims described you as a monster. The scale and enormity of your offending confirms this as an accurate description." The judge continued: "Rarely, if ever, have the courts seen such a campaign of rape as this, covering so many victims over a prolonged period." If this story has raised concerns for you, contact Lifeline on 13 11 14 , Beyond Blue on 1300 224 636 or the Suicide Call Back Service 1300 659 467. Telegraph, London