A postman admitted today that he groomed hundreds of children for sex over a five-year period, using social networking sites to court his victims.
Michael Williams, 28, from Penryn, Cornwall, pleaded guilty to 27 child sex offences when he appeared at Truro Crown Court.
He admitted three counts of grooming, eight counts of sexual activity with a child aged between 13 and 15, nine counts of causing or inciting a child aged between 13 and 15 to engage in sexual activity, four counts of causing or inciting a child under 13 to engage in sexual activity, and one count of voyeurism.
He also admitted two counts of making and possessing indecent images.
The former match secretary of Falmouth Town amateur football club also asked for some 460 similar offences to be taken into consideration.
Between 2005 and 2009 Williams pursued hundreds of schoolchildren, signing up to sites such as Facebook and Bebo, posting as a youngster.
He then carefully groomed his victims online, winning their confidence and often asking them to use an internet video camera, or webcam.
Detective Inspector Simon Snell said after the guilty plea: "He created a number of spurious profiles, portraying himself as a child and was making contact with children of the same age.
"He sent them questionnaires, asked about where they lived, asking for their mobile numbers, and if they had had sex. He is a manipulative and predatory paedophile."
Williams, who had also worked as a taxi driver, used all of his positions to bring himself in contact with the children, Mr Snell added.
Williams has been remanded in custody for psychiatric reports and will be sentenced on a date to be fixed.
Speaking outside court, Mr Snell added: "I hope he now understands the harm that he has caused to victims, their families and the many people who thought they could trust him.
"He is a predatory, manipulative and prolific offender.
"I hope he can reflect and if he wishes to talk to us about any other offences he should make contact with us."
The detective paid tribute to the bravery of the youngsters who reported the crimes.
"The investigation would not be where it is today without some very brave young people coming forward and disclosing to my colleagues in social services and the police exactly what had happened to them on the internet," he said.