A convicted sex offender obsessed with "panties and underwear" was caught offending online by police after he was targeted by paedophile hunters.
Morgan Green, 48, thought he had been communicating with teenage girls but had in fact been messaging with two adult decoys from paedophile hunter groups.
Norwich Crown Court heard he had been in conversation with an adult decoy who immediately stated she was 13.
John Morgans, prosecuting, said Green initially stated she was "too young" but he went on to manipulate the conversation around to a sexual context.
Mr Morgans said Green, who has an "obsession with underwear" had been asking her for pictures of her "in her panties".
In online conversations with another 13-year-old, also an adult decoy, Green again requested pictures before encouraging her to commit a sexual act upon herself.
Police were contacted and Green, who has a previous conviction for attempted sexual communication with a child, was arrested.
Green, from New Street, Cromer appeared for sentence on Monday after admitting two counts of attempting to engage in sexual communication with a child.
He also admitted attempting to cause or incite a girl under 16 to engage in sexual activity on November 19 last year.
Judge Andrew Shaw said Green was a "dangerous" offender who posed a "significant risk of serious harm" to children.
He imposed an extended sentence of 10 years and four months, made up of four years and four months custody and six years on licence.
Judge Shaw added: "People like you don't just happen upon these sites, you go looking for them".
Cathy McCulloch, mitigating, said the defendant, a father of three, was a man who had a "bit of a self-destruct button" but was "just so grateful they weren't real children".
She said he wanted her to say he was "very upset" and "very sorry" but accepted what he had done was wrong.
Green was also made the subject of an indefinite Sexual Harm Prevention Order (SHPO) as well as being put on the sex offenders register for life.
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