One of Britain’s most prolific paedophiles - who blackmailed a string of vulnerable victims including a girl who was ordered to eat dog food - has been jailed.

Dr Matthew Falder has admitted 137 offences, including blackmail, voyeurism and encouraging the rape of a child, relating to 46 complainants after being caught following an international inquiry led by the National Crime Agency (NCA).

The former King's pupil has been jailed for 32 years. Falder approached more than 300 people worldwide.

The 29-year-old, who set up hidden cameras at his parents’ home in Manchester , was arrested in June last year after three traumatised victims, who were tricked into sending him humiliating images, attempted to end their own lives.

Sentencing ‘warped and sadistic’ Falder for ‘a tale of ever increasing depravity’, Judge Philip Parker QC said: “As for your equally extraordinary sexual offending - no one who knew you above ground had an inkling of what you were doing below the surface.”

Branding him an ‘internet highwayman’, he added: “You wanted to assume total control over your victims.

“Your behaviour was cunning, persistent, manipulative and cruel.”

Former Birmingham University researcher Falder, originally from Knutsford, forced one victim to film herself licking toilet seats and eating dog food.

He set up secret cameras in bathrooms to record women and girls.

Falder also set up hidden cameras in publicly accessible toilets and at his parents’ home in Manchester, catching his unsuspecting victims on film, and using the footage to blackmail - and trade with others online.

Prosecutor Ruona Iguyovwe previously told the court that many of the images were then distributed on so-called ‘hurtcore’ websites on the dark web, showing material depicting sexual and physical abuse.

Falder was also a member of several ‘virtual communities’ of abusers.

One of his victims, speaking anonymously after his sentencing, described how their abuse had led to the breakdown of ‘all relationships’ in their life, and how they were now ‘scared to meet people’.

The operation to catch Falder, who used specialist software to hide his online accounts, was aided by The Government Communications Headquarters (GCHQ), the United States Homeland Security Department and law enforcement bodies in Israel, Slovenia, Australia and New Zealand.

Falder, of Harborne Park Road, Birmingham, committed the offences over an eight-year period.

He never met any of his victims, but instead manipulated them from afar by duping them into providing indecent images and personal details.

On his arrest, the former post-doctoral researcher in geophysics at the University of Birmingham asked officers: “What is it I’ve done?”

Then correcting himself, adding: “Supposed to have done.”

He then quipped that the list of suspected offences sounded ‘like the rap sheet from hell’.

Matt Sutton, NCA senior investigating officer, 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.

“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.

“This investigation represents a watershed moment.

“Falder is not alone so we will continue to develop and deliver our capabilities nationally for the whole law enforcement system to stop offenders like him from wrecking innocent lives.

“I commend the victims for their bravery and I urge anyone who is being abused online to report it. There is help available.”

Commenting after the sentencing, Dr Simon Hyde, headteacher at Kings, where Falder studied, said: “We are shocked and appalled to hear of this horrifying case. Our thoughts are with the victims and with their families.”