A gifted young academic who became a "warped and sadistic" paedophile has been jailed for 32 years.
Matthew Falder, 29, humiliated his victims and blackmailed them into performing ever-increasing acts of depravity on themselves and others, including the rape of a toddler.
The computer whizz-kid committed all his crimes online, hiding behind dozens of false identities on the dark web.
On some so-called "hurtcore" websites he was made a VIP member because of the ultra-depraved images he posted, granting him access to even more sickening material.
He targeted girls, women, boys and men, but never met his victims. Three of those he tricked into sending him humiliating images tried to kill themselves.
Birmingham Crown Court heard how one young girl was made to lick a toilet seat and eat dog food, and that a father was forced to rape and torture his two-year-old son – in what Judge Philip Parker QC described as "a tale of ever-increasing depravity".
He told "warped and sadistic" Falder: "You wanted to assume total control over your victims. Your behaviour was cunning, persistent, manipulative and cruel. The damage you did is ongoing and will never end.
"Victims know those images still exist on the computers of unknown people."
It took the UK's National Crime Agency (NCA) four years to identify Falder, track him down and arrest him, following a global investigation.
When they did, he was not what they were expecting.
They discovered he was a research physicist, public school-educated, and a star student from Cambridge University, where he was known as a party animal with many friends.
Falder's double life began as a voyeur when he hid cameras in the bathrooms and toilets of his fellow students and friends.
Later, he targeted teenagers, offering babysitting and dog-walking services for pocket money on the marketplace website Gumtree.
Posing as a depressed female artist called Liz, he chose the most vulnerable, offering them money for topless pictures, then threatening them with exposure if they did not send more explicit and humiliating pictures.
One male victim was blackmailed into eating his faeces and drinking urine.
And in an email to one 15-year-old girl, he said: "I wanted to offer you two choices.
"A) You take some more photos for me….. slightly different from before.
"B) I get upset, and instead of sending money, I send printouts of all the pictures you have done to your address, at many points in the future (in envelopes that your mother is likely to open)."
The victim told Sky News: "I didn't tell anyone. I was really… I was ashamed. Obviously you've heard what the pictures were like. They were awful. And I didn't want any of my friends to know that I wanted to do that.
"It was all online, through the internet. I felt that 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.
"I don't talk to my family anymore at all because, for me, I felt that they wouldn't understand and didn't understand what had happened to me."
Prosecutor Ruona Iguyovwe told the court how Falder showed "no shred of sympathy" for his victims, even when they told him they were considering taking their own life.
Instead, his reaction would usually be to "reinforce his demands".
Falder – one of Britain's most prolific paedophiles – had 70 different online identities, including EvilMind and 666devil, and boasted to victims that he would never be caught.
The NCA led a task force including US and Australian police, and even consulted the UK's spy centre GCHQ to uncover his true identity.
When he was confronted with his crimes after being arrested last summer at Birmingham University, where he was working as a researcher after finishing a doctorate at Cambridge, he told investigators: "That sounds like the rap sheet from hell."
The NCA's Matt Sutton said the investigation represented a "watershed moment".
He said: "In more than 30 years of law enforcement I've never come across an offender whose sole motivation was to inflict such profound anguish and pain. Matthew Falder revelled in it.
"His primary motivation was for power and control, suffering and humiliation. Believing he had superior intellectual and computational abilities, he was confident he could outwit law enforcement.
"I've also never known such an extremely complex investigation with an offender who was technologically savvy and able to stay hidden in the darkest recesses of the dark web."
Falder admitted 137 crimes, including encouraging rape, sexually exploiting children, blackmail and voyeurism, which were committed over an eight-year period.
His lawyer said he acknowledged the impact of his crimes on his 46 victims and had pleaded guilty, so sparing them the ordeal of giving evidence in a trial.
His wealthy family, from Cheshire, and his long-term girlfriend are said to be standing by him and have vowed to help rehabilitate him on release from jail.
A spokesman for the university where he had excelled said his crimes had "appalled and distressed" the Cambridge community, while the NSPCC has branded him a "despicable predator".
Gumtree also welcomed the conviction of Falder for his "appalling offences".
A spokesman said: "Our dedicated safety team has been working with the NCA in its investigation of this case for several years. We take the safety of our users extremely seriously and are committed to making the site as safe as possible."
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The judge told Falder he will have to serve two-thirds of the 32 years before he is eligible for parole in 2038.
Even then he will not be freed until the Parole Board decides he is no longer dangerous, and could have to serve the whole 32 years in prison.