A man who was working as a teacher at the time of his arrest admitted to possessing hundreds of pornographic images of children as young as four, many of them classed as the most serious on the internet.

And a BT employee possessed more than 500 indecent pictures, some of children as young as seven. Teacher William Bayes, 57, and BT employee Andrew Richard Walters, 33, pleaded guilty yesterday to 20 counts each of possessing indecent images of children which they had downloaded from the internet.

Bayes, of New Hey Road, Rastrick, worked as a teacher at Huddersfield Technical College when police arrested him on April 8, seizing his computer and 836 indecent images of children.

Of these, 289 were classified by police as levels four and five. The scale runs from one to five, where five are the most serious.

Some were films, up to 15 minutes long, of young girls performing sex acts on a man.

Prosecutor Stephen Gration told Dewsbury Magistrates that Bayes, grey-haired and wearing a dark suit, "got sexual pleasure from viewing it" (child pornography).

"When interviewed, he said he had never paid to access child pornography, although he used his computer for child pornography about once a week," said Mr Gration. "He was ashamed of what he had done."

Magistrates had looked at 20 images, 16 of which were of levels four and five.

They ordered Bayes to be sentenced at Leeds Crown Court on a date yet to be fixed.

The court also heard that Walters, of Stead Hill Way, Thackley, had looked at the child pornography "out of pure curiosity".

Dressed in a dark suit, Walters bowed his head through much of the hearing.

Police searched his home on March 23, seizing 511 indecent images of children which ranged from levels one to four in seriousness.

Ian Hudson, for Walters, said: "He is a man of good character, has never been involved with children, hasn't any of his own and has never worked with children."

The case was adjourned for sentencing until August 13. The two men were caught through the FBI-led Operation Ore which ensnared people who had downloaded child pornography on to their computers. Both men have to register with police as sex offenders.