A school lab technician was arrested after he left a memory stick in a staff room containing images of naked children, a court heard.

A female teacher at the Isle of Sheppey Academy in Minster put the USB stick into a computer to try to find out who owned it and was shocked to see the content.

It led to the arrest of Peter Holsten, who was found to have thousands of child sex abuse images and extreme pornography on his computer and other memory sticks at his home in Princes Avenue, Minster.

But the 71-year-old grandfather avoided a jail sentence after a judge said he would get longer supervision and sex offender treatment under a community order.

Holsten, now of Bellman Avenue, Gravesend, admitted three offences of possessing indecent images of children, two of possessing extreme pornography and one of possessing a prohibited image of a child.

He was sentenced to a three-year community order and ordered to attend a sex offender programme.

A sexual offences prevention order was imposed and his name will appear on the sex offenders’ register for five years.

Judge Michael Carroll warned that if Holsten breached the order 15 months imprisonment would be the starting point.

Prosecutor Bridget Todd said a teacher had been tidying up in the preparation room for a science classroom on February 5 when she found the memory stick on top of a shredder.

“She put it in the computer to ascertain ownership,” Miss Todd told Maidstone Crown Court.

“Unfortunately, when she did so she saw indecent images of children with their genitals exposed.”

When officers went to Holsten’s home the next day he told his wife: “The police have found a memory stick of mine with things on it I should not have. I’m sorry.”

He added: “If you do what I do you run the risk of getting caught. I got caught because I was careless.”

There were 4,313 images of children at various levels of seriousness, an extreme image of a woman having intercourse with a dog and 40 others where there was “risk of serious injury to a person’s genitals”, said Miss Todd.

Holsten, who resigned from the school, admitted to police he found the images exciting and had been addicted for about three years.

Judge Carroll told Holsten: “It is not just porn or kiddie porn or any other title attached to it. This is sexual abuse of young children. Those images cannot be created unless children are abused.

“There is a lack of reticence in performing the sordid acts which titillated you. If people like you were not so ready to subscribe or download, the real abusers would be out of a job.

“It is not just porn or kiddie porn or any other title attached to it. This is sexual abuse of young children. Those images cannot be created unless children are abused" - Judge Michael Carroll

“That is the upshot of this. It does not surprise me you thought there was a good chance you would be going to prison today.”

The judge praised Holsten for getting help with his addiction but said it was a pity he had not done so before he was caught.

“I do not think it is in the public interest that I send you to prison today,” he continued.

“A prison sentence would be limited to a two-year operation period. It is in the public interest that you are kept under supervision in the community for as long as possible.”