Gavin Wright of Norfolk Way, assaulted a girl multiple times 16 years ago.
He was sentenced to seven years in prison at Chichester Crown Court. The girl then aged 10 or 11 was subjected to a number of assaults in West Sussex over the course of a year.
He was sentenced following conviction for six sexual assaults and for possessing and distributing indecent images of children.
Detective Constable Ellen Jones of the West Sussex Safeguarding Investigations Unit said: "Wright came to know the young and vulnerable girl whilst living in East Grinstead, gradually gained her confidence and then systematically abused her for his own sexual gratification.
"When we arrested Wright we found in his possession vile indecent images of children being abused.
"While we were investigating his sexual assaults, our colleagues in the force's Paedophile Online Investigation Team (POLIT) were investigating his more recent though completely unrelated online activities. They had found that another sex offender was messaging him and sending these images who he then sent on to others.
"So he received four-and-a-half years for the sexual assaults and an additional two-and-a-half years for the online offending.
"He will also be a registered sex offender for life, and was given a Sexual Harm Prevention Order (SHPO) to last until further notice, severely restricting his access to children and digital devices.
"In addition he was given a court Restraining Order prohibiting him from any contact with his victim."
The victim who finally found the resolution and courage to tell the police, told the court: "My reason for reporting the incident was to expose him for what he is to the world – manipulative and dangerous - and ensure that what I went through is never allowed to be repeated and affect the life of any other young person. No person deserves to have any of this happen to them. He deserves to face the consequences of his actions now and in the future."
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