A predatory sex offender who used the internet to abuse girls from around the world is starting a five year jail sentence today.

Robert Sadd, 37, admitted sexual activity with a 15 year old girl he met through a website and after grooming her and sending her sexually explicit messages he arranged to meet up for sex with her at a hotel in London, Norwich Crown Court heard.

Police also found thousands of indecent images of children on his computer when his home in of North Everard Street, King's Lynn, was searched. The court heard Sadd had got the girl to send him explicit photos of herself and had taken an indecent photo of the girl when they met on London.

Andrea Lock, prosecuting, said there were 7,262 indecent images of children and 9,992 prohibited images found on his computer equipment. Jailing Sadd, Recorder Guy Ayers told him: 'You have an unhealthy and inappropriate interest in underage girls.'

He said that Sadd had visited a sex site in the hope of meeting a young girl, before exploiting her vulnerability and engaging her in conversation about sexually explicit matters.

'You at the time were 36 years of age,' he said. 'You used your experience and knowledge of life to take advantage of her.

'There was a very clear element of grooming and you taking advantage of a young girl to satisfy your desires and what you saw as your needs,'

As well as banning Sadd from working with children, the judge also made him subject to a sexual offences prevention order under which he cannot have unsupervised contact with any female under 16.

Isobel Ascherson for Sadd, said that the girl involved was just short of her 16th birthday and said he did have genuine affection for her.

She said there was no evidence of him having physical contact with any other girl who was underage.

'This man has got himself in the most extraordinary criminal position by his behaviour and his pornography obsession,' she added.

Sadd's activities first came to light in November 2011, when a father in America caught his teenage daughter communicating with him online. The communication had become sexual, and the father notified the authorities and the NCIS began their inquiry.

NCIS contacted the Child Exploitation and Online Protection Centre (CEOP) in the UK with their findings, who in turn contacted Norfolk Constabulary and a warrant was executed on 13 March 2012 where evidence was seized.

After the hearing officer in the case, Det Con Tracy Billing, said: 'Sadd is a predatory sex offender, taking advantage of modern technology to abuse girls across the world as well as physically in this country. He had in his possession a vast amount of indecent and prohibited images, internet crimes such as these are far from victimless where every image depicts the very real abuse a young child has suffered. He will be spending a considerable time in prison and will remain on the Sex Offenders Register for life so that the very real danger to children and young people he poses can be managed.'

Det Sgt Sally Money added: 'Norfolk Constabulary, like the other agencies involved in this investigation, will do everything within its power to protect victims who are subjected to these potentially life changing acts of indecency purely for the gratification of others.

'We would also encourage parents to take an interest in their children's online activities. Young people often have no idea who they are really chatting to and could be unwittingly putting themselves in a vulnerable position.'

The Child Exploitation and Online Protection (CEOP) Centre's 'Thinkuknow' website provides information, advice and guidance for children and parents on how to stay safe online.

Paul Phillips, CEOP's head of operational delivery, said: 'The prison sentence Sadd is starting today should act as a deterrent to those who think they can abuse children via the internet – you will be caught and punished.'