A young Tasmanian girl has been pivotal to the arrest of an international pedophile.
Police discovered more than 800 homemade images and videos on the computer of British man Robert Hunter, 35, who has been jailed for 14 years.
From 2010 to 2012, Hunter posed as a teenager over the internet, luring young girls via a series of online aliases.
He was arrested in December last year but continued to offend.
It was then that a girl from Tasmania spoke up and contacted police, who were then able to trace him to his Middlesbrough home.
In sentencing in Teesside Crown Court, Judge Peter Bowers said it was one of the most serious cases on internet abuse that the courts had dealt with.
``It's a warning to all parents of teenage children of what can be done via the internet,'' he said.
``The public will be disgusted by how you have behaved even after you had been arrested and bailed.
``It represents callous and sadistic exploitation of a number of girls over a number of years.''
Hunter used Facebook, Skype and MSN to abuse victims - some as young as nine - across Europe, Asia, Canada and the US.
He encouraged them to expose themselves and perform sex acts via webcam, often by posing as pop star Justin Bieber.
Occasionally, he would use the videos they sent him to blackmail them into submitting further to his demands.
He pleaded guilty to 30 offences, including 15 charges of causing or inciting a child to engage in sexual activity and 14 of making indecent photos of children.