- Video report by ITV News correspondent Ben Chapman
Matthew Falder relished his depraved double life.
To his friends, he was a talented geophysicist and the "life and soul of the party".
But in the darkest corners of the internet, he was known as “Evilmind” and “666devil” - and on a journey to becoming one of Britain’s most sadistic sex offenders.
Falder, who was today sentenced to 32 years in prison for more than 100 offences, degraded and humiliated girls, boys, women and men during an eight-year campaign of abuse.
His voyeurism began at Cambridge University in 2007 where he set up hidden cameras to secretly film his fellow students in the bathroom.
But Falder’s warped desires soon ensured he broadened his search for victims.
Posing as a depressed female artist called ‘Liz’, he scoured internet sites such as Gumtree and duped dozens of people - including anorexic teenagers into sending him explicit photographs of themselves.
Once in possession of their personal images, Falder then proceeded to blackmail them into sending increasingly graphic pictures - threatening to expose their pictures to their friends and families if they refused to comply with his demands.
Some were forced to lick toilet seats and eat dog food; some told to eat their own faeces.
His abhorrent acts also included encouraging the rape of a four-year-old boy and accumulating material showing babies being tortured.
Hiding behind his online personas, he would then distribute images and videos on the dark web, where he thrived on his status as a "VIP member" of the online paedophile underworld.
Falder eluded the authorities for years, bragging to his victims that he would never be found.
But the 29-year-old was eventually unmasked, following a long-running investigation by the National Crime Agency and with help from GCHQ, the government's surveillance agency.
When he was arrested in his office at Birmingham University, where he worked as a researcher, he told police that the list of his suspected offences sound like "the rap-sheet from hell".
Police and prosecutors agreed; they describe the Falder case as among the most disturbing and harrowing they have ever dealt with.
"I've never seen a human being who was prepared to go to such lengths to do such damage to a large group and to put such a significant investment in staying hidden," Matt Long, from the NCA, told ITV News.
He was charged with 188 offences relating to paedophilia, voyeurism and blackmail, later pleading guilty to 137 charges against some 50 victims.
It took over 35 minutes to read out all the charges against him in court in October last year.
Falder's actions had a devastating, life-altering impact on his victims.
Three attempted suicide; others have self-harmed. Psychologists say many will struggle to recover from the trauma.
“I'll always be scared of meeting new people,” one of Falder’s victims said.
She was just 15 when she was tormented by Falder after posting an advert as a babysitter to earn money while studying for her exams.
She describes being bombarded with messages every day and living in permanent fear that Falder would share her compromising images with her loved ones.
"Every day when I woke up, there would be a message; when I came home from school, there would be a message,” she said.
"When I wasn't actually talking to him I was worried about when the next message was going to come through."
She added: “I was ashamed, and obviously you've heard what the pictures were like, they were awful and I didn't want any of my friends to think that I wanted to do that. I felt like no-one would understand because there was no-one there holding a knife to me saying 'you will do this', even though it felt like that."
Falder’s abuse led to the total breakdown of her relationships with family and school friends - none of whom she now speaks to.
"It's hard to have a family and a partner and friends when you don't trust them; eventually they get upset that you don't trust them and they just leave."
Describing her hopes for the future now Falder is behind bars, she said: "I hope one day I can rationalise the fact that not everyone wants to hurt me."
- If you are affected by any of the issues raised in this article or are concerned about an individual, you can contact the NSPCC