Philip Thompson, who lived at home with his mother, was responsible for a website that catalogued around 250,000 images of child abuse. The 27-year-old's arrest prompted one of the biggest ever seizures of pornography in the UK.

Teesside Crown Court heard today that the internet-based child abuse ring reached at least 33 countries over the five years Thompson was involved.

Judge Michael Taylor said Thompson posed a very “significant risk” to the public, but he was given an indeterminate sentence with a minimum of just three years and nine months. Under the terms of an indeterminate sentence, he will have to prove to a parole board that he is no longer a danger to the public before he can be freed.

“You have shown that you are a very dangerous individual indeed. I consider that you pose a very significant risk to the public and you are a dangerous offender,” said the judge.

Thompson, of Gooseport Road, Stockton-on-Tees, Cleveland, pleaded guilty to 27 charges, which included 16 counts of making indecent photographs of children, seven counts of distributing indecent photographs of children and one count of causing or inciting a child under 13 to engage in sexual activity.

Prosecutor Harry Hadfield said that police raided Thompson’s home in February this year and recovered two desktop computers and a laptop.

“Forensic analysis by computer experts established that the defendant had 241,000 indecent photographs of children, being one of the largest seizures of indecent photographs in the UK,” he said.

Thompson was the moderator for an online forum used by paedophiles across the world to trade in child pornography, the court heard.

Mr Hadfield told the court: “The defendant’s role was to police the website, which gave him the opportunity to transfer these images to his computer.

“The evidence recovered from his computer showed he had amassed a vast collection of indecent photographs of children.

“It appeared the defendant kept some of the most serious images to use as trading chips.”

Of the near 250,000 images on Thompson’s computers, more than 3,000 were of the worst kind of child abuse, rated as levels four and five by officials.

During police interviews, Thompson admitted sharing the pornographic images with thousands of people across the world.

“The Crown would say that this collection of indecent photographs and the subsequent police investigation revealed that this defendant has been involved in the distribution of these photographs for the last four or five years,” Mr Hadfield said.

He added that 51 arrests had been made as a result of the investigation into Thompson and inquiries were continuing.

The operation that led to the conviction of Philip Thompson yesterday is expected to identify 10,000 users of the internet forum of which he was a key moderator and administrator.

The seven members of Wonderland had traded 120,000 images. Thompson had more than twice that number stored on his computers. Although the scale of the online paedophile problem appears to be growing and a significant number of abusers evade justice, law enforcers are not in complete despair.

In 2001 the lament from police trying to grapple with the most horrendous area of the developing world of e-crime was that by the time they caught up with the technological trickery of one paedophile ring, another would be using more advanced methods of encryption and disguise. However, massive investment, pioneering techniques and strong international co-operation has tilted the battle back in favour of the investigators. Highly trained officers routinely go online posing as child abusers eager to gain access to members-only chat rooms where the worst imagery is exchanged.

Last year investigators arrested the kingpin of one network while he was online and took over the running of his site for ten days to amass evidence against hundreds of suspects.

Techniques developed in the fight against terrorism or organised crime are increasingly deployed — including physical surveillance of dangerous paedophiles.

For the men and women involved, this is a zero-tolerance area of crimefighting. They even demand that no one uses the words “child pornography” in relation to the harrowing images that they find. Every photograph, they emphasise, captures an actual situation in which a child has been abused.

Teacher Christopher Neil, 32, posted pictures of himself abusing at least a dozen Vietnamese and Cambodian boys. But the pattern he used to hide his face in the pictures was unscrambled by Interpol and publicised.

Investigators received hundreds of tips which led to Neil's arrest in October last year.

Snared: Christopher Neil arrives at court in Bangkok to be sentenced today

Neil, from British Columbia, Canada, was sentenced to three years and three months in Bangkok, Thailand, for sexually abusing a boy of 13.

He still faces a series of charges over the victim's younger brother, who was nine at the time, and has been warned he could eventually be sentenced up to 20 years.

The judge handed down a sentence of six-and-a-half  years but said she was cutting that in half because Neil had confessed.

He was also ordered to pay a 60,000 baht (£955) fine after he pleaded guilty to abusing the Thai teenager, but pleaded not guilty to abusing the boy's younger brother.

Other charges he has yet to face trial for include sexually abusing a minor, videotaping the alleged abuse, taking a child without parental consent, and holding him against his will.

The younger child claims Neil paid him £7.50 to £15 to perform a sex act in 2003. That trial resumes on October 7.

When asked to comment, Neil, who appeared in court wearing orange prison garb and shackled at the ankles,  only said 'OK'  as he was taken away.

He will serve his sentence in a Bangkok prison

Swirly faced: Christopher Neil was tracked down after Interpol unscrambled digital images from about 200 internet photos

His translator, Feros Mia, told reporters he had shown no emotion in court and that he was 'fine with the verdict'.

Rosalind Prober, president of the Canadian child rights group Beyond Borders, said: 'This is the first, baby step for Christopher Neil in terms of having him held accountable for the international sex crimes he is accused of committing.'

Interpol secretary general Ronald Noble hailed the worldwide cooperation that brought Neil to conviction.

He said: 'Neil's arrest came as a result of extensive coordinated work between Interpol and police in several countries first to identify Vico as Christopher Paul Neil, and then to bring him to justice.

'Most importantly, the arrest and conviction of Neil, a Canadian, for the sexual abuse of children in South-East Asia demonstrates that Interpol will use all available legal tools, including obtaining media and public support, to track down these predators wherever they may be found.'