POLICE have vowed to make changes after a high-risk paedophile was left to walk free as crucial evidence was lost for two years.

In April 2014, Karl Marper was arrested for downloading and sharing images and videos of men binding and having sex with boys as young as six.

But Marper, who had multiple previous convictions for similar offences, was not charged until October 2016 however, 30 months after his first arrest.

Thames Valley Police (TVP) outsourced evidence to a private company which then couldn’t find the images and videos, allowing the 48 year-old to walk freely around Reading until a second company put together a successful case.

The force admitted the system had already changed. A TVP spokesman said Marper was on bail throughout the two years and forbidden from being alone with a child and going on the internet.

“The issues of delay and the quality of the product provided in the forensic examination of the computers in this case are clearly of concern and were identified as such at the time. This directly led to the digital forensic review of the R v K Marper case devices by a different company, which provided the evidence which led to this conviction,” they said.

“Thames Valley Police has already reviewed and revised our processes as a result of this case.

“The systems we have put in place and the robust management of the outsourcing means we are getting a quality service in a timely manner.”

Although Marper committed no further offences between his arrest and eventual sentencing, on February 10 at Reading Crown Court Judge Joanna Cutts QC said there was a high chance he would physically abuse a child in the future.

“This is a very concerning case,” she said.

“You have not committed a contact offence but there is concern that you will.

“It seems that you have been in direct contact with two convicted offenders you met in custody, one who was sentenced for the rape of a 14 year-old boy.

“During a treatment programme you told your offence manager that you were at risk of committing a sexual contact offence with a young boy. You also talked of having sexual fantasies about young boys on trains.”

When Marper, who has multiple sclerosis and was a full-time carer for his wife, was eventually brought to court, he was convicted for four offences relating to child pornography.

He was found with 86 of the most serious videos and images and a peer-to-peer folder to share material with like-minded offenders.

Speaking in defence of Marper, lawyer Kim Preston said: “The court is dealing with somebody who is not only very concerned about the offences he has committed, but also the feelings that he was experiencing.”

On February 10 Karl Marper, of Northumberland Avenue, Reading, was sentenced to six years in prison for four counts of possessing indecent images of children.

He was also given a Sexual Harm Prevention Order and will sign the Sex Offenders’ Register for life.