35-year-old Luiz Da Silva Neto has been found guilty of drugging and assaulting two men at a luxury house in the Oxfordshire countryside.
He used the date-rape drug GHB on the men in separate incidents last year, before going to commit the offences.
Da Silva Neto, from Wandsworth in south London, had been managing the property, which was being rented out as a holiday let in the village of Middle Barton.
Oxford Crown Court heard how his first victim, a man in his 30s, knew Da Silva Neto through his work, and had been at the cottage to help with decorating.
Luiz Da Silva Neto during his police interview
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A police video-taped interview was played to the court, in which the victim described feeling strange after being given a drink by the defendant.
“I had to lay down instantly,” he said. “I felt like my head is going somewhere.”
He said he felt “knocked out, like heavy headed, like sleepy.”
The victim said he lay down on a bed to sleep, before waking up sometime later and realising he was being sexually assaulted.
“I went to bed with my clothes on and when this happened I was naked.”
In the video interview, the victim became distressed as he told officers he was too weak to do anything to fight back against Da Silva Neto.
“It was so disgusting and creepy. I didn’t know what to do. I didn’t have the power to do something.”
The luxury cottage in Oxfordshire where the incidents took place
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Da Silva Neto would often look for men at night, especially those that had had too much to drink.
Mobile phone video was played to the court, which was shot by the defendant, as he went looking for potential victims in public toilets.
The second incident took place in Chelsea, west London, in December last year.
The victim had been on a night out in a local club and had been looking for a taxi home when he was approached by Da Silva Neto.
He told police he remembered very little of what happened next, other than drinking a small amount of liquid given to him by the defendant.
He told authorities he woke up in a strange cottage, 70 miles from London, having been raped.
Police believe it is likely that Da Silva Neto used the date-rape drug GHB. Only a tiny amount is needed to render a victim unconscious.
Da Silva Neto admitted to authorities that he used the class-B drug for recreational purposes.
In a videoed police interview after his arrest, the defendant claimed the interaction between the two men had been completely consensual.
He told officers: “I was in the King’s Road. I stopped to get some cash out and I started talking to this guy as well.
“And he told me he’d been to the club.. and like do you want to have a drink together, whatever.
“He’s like yeah. He’s like, I’m married but yeah. And we decide to go have a drink, that’s all.”
Raffles nightclub
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Detective Inspector James Holden-White, who led the investigation into Da Silva Neto said that such incidents are still relatively rare, but the use of drugs like GHB can be extremely dangerous.
He said: “What I will say about GHB is, it's odorless. It’s colourless.
“We're talking millilitres of liquid or milligrams diluted into milliliters of liquid. Very small amounts, which can be easily disguised in a drink.
“Small doses used recreationally can have a euphoric effect. It can reduce inhibitions and increase the libido and that's why it's been used recreationally for some time.
“But slightly more can affect someone's capacity to form a memory about what's happened to them. It can incapacitate people.
“And really not a great deal more than that could be sufficient to be a fatal dose, so it's a really dangerous drug to to be playing with.”
The serial killer Stephen Port used higher doses of GHB on his four young male victims at his home in Barking, east London. He later dumped their bodies in a graveyard next to his home.
The UK’s most prolific serial rapist Reynhard Sinaga also used GHB to drug and attack his young male victims.
Authorities believe he probably raped more than 200 men since 2005.
He is now serving life in prison.
Police say Da Silva Neto appears to have deliberately targeted straight males, perhaps believing they would be too embarrassed to report the assault to authorities.
Inspector Holden-White appealed directly to anyone who may be a victim, to come forward.
He said: “We keep an open mind and we continue to investigate his activities.
“It is entirely possible that there are other offenses out there, and other victims who have not as yet been identified or identified themselves to us.
“So what I really want to do is encourage victims to come forward and have the confidence to do that.
“The conviction of somebody for offenses like this is quite often the platform from which other people will have that confidence and feel empowered to come forward and feel safer to do so.
“Or just to seek support. We can help them access that. We have officers specially trained in investigating serious sexual offences, who can assist them in providing an account.
We can also preserve people's anonymity through that process, as we have done in this case."
Luis Da Silva Neto will return to Oxford Crown Court for sentencing at a later date.