JAKARTA - For two and a half years, the young Indonesian man named as Britain's worst rapist prowled the bars and restaurants of Manchester in search of young male victims.

Reynhard Sinaga, 36, lived just a few doors away from the popular Factory nightclub in Princess Street, in central Manchester, and the club became his favourite hunting ground.

Police said Sinaga often went out after midnight, and in one of the CCTV recordings, is seen returning to his flat just 60 seconds later with a young man who was later raped, BBC reported.

Sinaga is believed to have used different ruses - offering a place to wait for friends or to charge a mobile phone - to lure about 190 victims to his apartment. Most of them were in their late teens or early 20s, and had been out drinking before he approached them in the streets.

Many of Sinaga's victims recalled he gave them a drink - which he once described in a WhatsApp group with friends as "secret poison" - when they went to his flat. He raped them after they passed out, filming the abuses on his two mobile phones.

One such clip showed a victim not stirring despite a mobile phone ringing at full volume in the background, The Guardian reported.

The prosecution said that the men were drugged, possibly with gamma-hydroxybutyric acid, better known as GHB or liquid ecstasy, or other substances with the same effect.

Sinaga was sentenced on Monday (Jan 6) to 30 years' jail for 136 rapes after he was found guilty of 159 charges.

Police believe Sinaga, who was arrested on June 2, 2017, would have carried on had one of his victims not woken up during an attack and called 999.

Following Sinaga's arrest, police discovered footage in two iPhones showing him raping scores of apparently sleeping young men.

When Greater Manchester police examined Sinaga's digital devices, they discovered 3.29TB - equivalent to 250 DVDs - of extremely graphic material depicting sexual assaults. In one case, the assault lasted for eight hours.

The victims did not know they had been raped until police tracked them down following Sinaga's arrest. They remembered Sinaga as a good Samaritan who had helped them out.

There were so many victims that his case took four separate trials with the first trial starting in June 2018 and the last one ending in December last year. None could be reported until restrictions imposed to avoid prejudicing juries were lifted on Monday.

The case has shocked many in his home country where homosexuality is still taboo, with many condemning the abuses as evil and depraved.

The University of Indonesia, which confirmed Sinaga was an alumnus, condemned his acts as "insolent, illegal and inhumane" and expressed its sympathy to the victims of his assaults.

Sinaga lived in the UK off money wired over by his father, a wealthy Indonesian banker who owns property businesses. Footage taken by the BBC showed his family's luxury house in Depok, West Java.

Born in Jambi, Sumatra, in February 1983 to a Catholic family, Sinaga was the eldest of four children. He attended a number of private schools and graduated with a degree in architecture from the University of Indonesia in 2006 before going abroad to study.

His parents had wanted to marry him off to a girl of their choice in Indonesia.

He went to the UK in 2007, when he was 24, on a student visa to pursue a masters' degree in planning and then sociology at The University of Manchester, graduating in 2011.

Sinaga, who was described as looking younger than his age, had a lot of friends in Manchester. But despite his boasting about his frequent "conquests" to his WhatsApp chat group, nobody suspected that he was a serial rapist.

"He was very flamboyant, had highlighted hair and was very camp," one man who went out regularly with him was quoted as saying by The Guardian.

He added: "He was always out, always going on holiday. We wondered where he got his money because he never seemed to work."

While living in Manchester, he later commuted to the University of Leeds, where he undertook his PhD degree in human geography. The school suspended him after his arrest in 2017 and expelled him after his first trial in 2018.

While in the UK, he worshipped at a liberal Anglican church close to his flat.

Members of the church provided the court with a reference.

"He did go to church and did some voluntary work, assisted with the service and with some classes too, with teaching. He sees himself as openly gay. He liked the fact that the church accepted him as an openly gay man and as also being foreign as well," Detective Inspector Zed Ali, the senior investigator in the case, was quoted as saying by the Manchester Evening News.