A Red Cross first-aider was found to have a staggering collection of more than half a million child porn images, a court heard today.

The images, both photographs and videos, were in all five categories of seriousness and a judge said: "Words can hardly describe them, abhorrent is the best word."

There were so many images that officers from Merseyside's high-tech unit stopped categorising them after counting 181,407 photos and videos.

They were found at the Wirral home Andrew Davies shared with his mother on Davies' tower computer and discs and some, unknown to his mother, on her laptop.

Davies, who admits to being "obsessed" with such images, was bailed after the find at the house in Leasowe, on January 27 last year.

But just five months later police raided his new home after being alerted by a shocked TV aerial installer.

He was working at Davies' home in Wood Lane, Greasby, and after discussion about Davies' satellite receiver, known as a Dream Box, which has hard drive storage facility, Davies asked him to guess what he had been watching that day.

The installer suggested a Man Utd game but Davies replied: "child porn".

When he saw his face change, Davies then added: "It's all right, it's okay. It was Chinese kids", said Joanne Maxwell, prosecuting.

The engineer left and immediately called police to tell them of the conversation, and Davies was re-arrested the following month in June.

Officers found three discs in his bedroom which again involved images in all the categories, including the most serious.

Davies said they had been at his previous home in the loft space and had been overlooked during the previous raid.

Miss Maxwell told Liverpool Crown Court that 40-year-old Davies first came to the attention of police after the American authorities found he had been using a file-sharing website to download child porn.

Davies, of Liscard Road, Wallasey, pleaded guilty to 17 offences of making indecent images.

"When he was interviewed he was extremely candid and accepted responsibility for downloading images," said Miss Maxwell.

The court heard he had been a Red Cross first-aider but had been suspended when the offences emerged and later resigned.

Jailing him for 15 months, Judge Mark Brown pointed out that under the Sentencing Guidelines Council, the maximum he could impose was two years but he had to give him credit for his guilty plea.

He ordered him to sign the Sex Offenders Register for ten years and made an indefinite Sexual Offences Prevention Order.

"Any right-thinking person listening to the facts of these case would be horrified and appalled to hear what sort of abuse that the children who are depicted had to endure when these images and movies were being made," said Judge Brown.

"If there were not persons such as you then there would not be a market for these sort of images," he added.

John Weate, defending, said: "Being obsessed by these images has not resulted in more serious crime such as physical crime."

He has sought help for his problem and will take advantage of any opportunities offered to him.

He is an isolated individual and because of the offences his relationship with his mother has become strained, said Mr Weate.