YORK'S top judge warned teenagers about the dangers of online child sexual images as he sentenced a young student.

Joshua Simpey, a first-year undergraduate, may find that some careers are closed to him and may be unable to travel to some countries because of his internet activities from the age of 13 to a few days before police knocked on his door when he was 17, York Crown Court heard.

The 18-year-old, of Deer Hill Grove, Clifton Moor, pleaded guilty to 16 offences relating to indecent, prohibited or extreme internet images of children, some of whom were toddlers.

Robert Stevenson, prosecuting, said police found 1,637 indecent child sex pictures on Simpey's computer including 204 assessed as being of the two most serious levels, 57 prohibited images and three extreme images. They also found 30 illegal videos including 26 of the top two levels. Half the material had been deleted.

The Recorder of York, Judge Stephen Ashurst, said: "It is important people, particularly in your age group, understand that accessing this material is likely to bring them into conflict with the police.

"The fact that you have been publicly exposed and shamed over what you have done is part of your punishment. You are an intelligent young man. You have career aspirations some of which may no longer happened as a result of your convictions.

"It is sometimes not appreciated, particularly by young people that a conviction for this sort of offence may have a bearing on whether you are able to travel to certain countries in the future. That is a price you will have to pay for your decision to download this particular type of material."

Simpey was given a community order with two years' supervision and an internet sex offenders' rehabilitation course, put on the sex offenders' register for five years and made subject to a sexual offences prevention order restricting his use of the internet and to children under 16.

His barrister Glenn Parsons said he couldn't explain why he had done what he had done. He was a gifted student studying science.