DORSET Police officers investigating Operation Ore porn cases in the county say none of their investigations have involved a prosecution witness who has been blamed for the collapse of the Soham detective's trial.

Detectives investigating the numerous names connected with the worldwide child pornography network say they did not access the help of any outside experts, in particular Brian Underhill.

Mr Underhill, a traffic policeman-turned-computer-crime expert, was involved in more than 600 of the 1,600 prosecutions brought by British police under the Operation Ore crackdown on paedophile websites.

His flawed evidence, which forced prosecutors to drop charges against Cambridgeshire detective Brian Stevens, is set to bring a flurry of appeals from people convicted on his evidence in the past.

It will also mean that hundreds of cases will have to be urgently reviewed.

A list of 7,000 names, all men, was given to police nearly a year ago after a child pornography network with access to 5,700 sites was uncovered in Texas.

Detectives in Hampshire and Dorset refuse to reveal the specific number under investigation but Operation Ore has closed in on suspects.

Bournemouth church organist Nigel Hannibal was one of the first suspects arrested during the crackdown.

The former organist and elder at Trinity United Reformed Church in Charminster was jailed for five months by Bourne-mouth Magistrates in February.

Police raided his Rownhams Road home after his name appeared on the FBI list of suspected sex offenders. They found graphic images of children aged four to 16 among thousands of pictures of youngsters dressed in underwear on his computer.

A Dorset Police spokesman said yesterday: "Dorset Police has undertaken a number of investigations as part of the national operation known as Operation Ore.

"In all of these investigations, the computer- based element of the investigation has been conducted by the force's own high-tech crime unit. Dorset Police has made no use of outside computer experts or advisers."