A PRISON worker alleged to have committed sex acts while watching pornography with young girls wiped his computer account just two days before it was seized by police, a court heard.

John Cornwell claimed he was merely trying to improve the performance of the computer, having downloaded a program from the internet.

The 53-year-old, a support officer at Northallerton Young Offenders' Institution, denies 13 charges of indecent and sexual assault, and sexual activity in the presence of a child and is on trial at Teesside Crown Court.

Detective Sergeant Stephen Days, of Durham police, said he made a further analysis of the computer seized following Mr Cornwell's arrest to see if there was any pornography which could be recovered.

He found a program had been installed which was used to delete internet histories.

This had last been used on May 1 last year - two days before police seized the computer.

Det Sgt Days said no files could be found, except what were described as "fragments" from two porn sites Mr Cornwell admitted he had visited.

The defendant, of West Auckland Road, Darlington, was asked if he had used the program to rid the computer of pornography.

But he denied this and said it had been used merely in an attempt to speed up the computer.

Mr Cornwell told his barrister Tom Mitchell that he had watched some hardcore pornography "two or three years ago", but not recently.

Mr Mitchell asked the defendant whether he was alone or not when he watched the pornography.

He replied: "Definitely alone".

The defendant, who has worked at Northallerton YOI for 20 years, also denied placing the hands of one of the complainants on his penis.

The court has heard how one of the alleged victims had previously admitted making up an allegation against Mr Cornwell after she apparently took inspiration from reading a gossip magazine.

The trial, which concerns historic sex allegations, continues.