A man wrongly accused in Britain's largest ever child pornography investigation has won damages in the High Court after an eight-year legal battle.

Jeremy Clifford, 51, from Watford, was arrested and falsely charged in 2003 as part of Operation Ore. His credit card details had been found among those of thousands of British people on a list maintained by Landslide, a commercial provider of illegal pornography based in the US.

Hertfordshire Constabulary seized a computer that had belonged to Mr Clifford and discovered 10 illegal thumbnail images in its temporary internet files folder.

However, a senior High Court judge found on Friday that the arresting officer had been told by a computer forensics expert that the images were not sufficient evidence to charge.

"The images could have been received unsolicited by and even without the knowledge of the operator of the computer, for example as 'pop-ups'," said Mr Justice Mackay.

Despite this, the officer, Detective Constable Brian Hopkins, pressed three charges of possession of indecent images of children. Mr Justice Mackay said he cut a "rather pathetic figure" in the witness box, having initially claimed he could not give evidence because of a psychiatric condition.

The judge found that Mr Hopkins, who has since left policing, not only had "no honest belief in the possession charges when he caused them to be brought against [Mr Clifford]", but did so "to protect his own position".

The finding was based on evidence the court heard from an internal investigation launched after Mr Clifford was formally cleared of all the allegations before trial. It found that Hertfordshire Constabulary’s forensics expert, George Fouhey, had advised against pressing charges.

"At no time did Mr Fouhey change his evidence," it said.

"He advised against charge. It was overruled in favour of charging with possession of the images in order to support a separate stronger charge. This separate charge was subsequently dropped. The remaining possession charges were then left in an unsupportable position."

The false charges led to depression, the failure of Mr Clifford’s business retailing professional film supplies, and, the judge said, "a destructive effect on his own feelings of self worth, his relationships with his own wife and family". He was awarded damages of £20,000 – plus costs which will run to hundreds of thousands of pounds – for malicious prosecution and misfeasance in public office.

Mr Clifford's solicitor, Andre Clovis of Tuckers Solicitors, criticised the way Hertfordshire Constabulary defended the complaint given they had known there was no evidence to charge.

"In my opinion it is an absolute disgrace that the police have been allowed to spend huge sums of public money recklessly and without apparent check or merit attacking Mr Clifford, in order to deflect from their own shortcomings," said Andre Clovis of Tuckers Solicitors.

"This course of conduct caused costs to escalate. There appears to be no control mechanism over police spending in such circumstances, but this does not mean that the Chief Constable and his legal department should not be called to account for their actions."

A spokesman for Hertfordshire Constabulary said: "Legal advice was taken beforehand and it was advised and expected that we had a reasonable chance of winning our case.

"We will seek to learn from this case and service improvements have already been implemented in the years since this case started."

The case has raised questions about the standard of evidence that triggered some Operation Ore investigations.

Not only were the illegal images in temporary internet files, but computer forensics evidence suggested Mr Clifford's credit card details had appeared on the Landslide database of as the result of fraud. He had complained about unauthorised payments and been refunded, the court heard.

Mr Justice Mackay agreed with the defence computer forensics expert, Duncan Campbell, that there was therefore "no evidence" that Mr Clifford was a "habitual seeker" of child pornography, as Hertfordshire Constabulary had advanced as a matter of fact.

Mr Clifford, who now works in a separate area of the film industry, now plans to appeal for greater damages. He is also considering complaints of alleged perjury against Mr Hopkins and to legal regulators over the conduct of Hertfordshire Constabulary’s lawyers. ®