Specialist officers hampered by fire that destroyed records

Detective Sergeant Andy Kenyon, of North Yorkshire Police's protecting vulnerable persons unit, said: "We had an initial report, a single report, relating to Mr Fetcher and from there the inquiry expanded over a period of time."

Despite rumours about the man dubbed "Fletch the Letch", "we had to go on pure fact, and have gone from one lead to another," he added.

Officer spoke to many people: "Any person whose name was mentioned and proved relevant to the inquiry," he explained. "Bearing in mind the investigation related to offences 20 to 30 years ago, we spoke to the victims and corroborated their stories as best we could."

They also pored through school records – registers, and attendance records to identify dates and establish when the people involved were at school.

A fire at the school several years ago, before the investigation began, destroyed some records, hampering the investigation. The police do not believe it was linked to the inquiry.

The investigation also only concentrated on relationships with girls under 16 – any relationships with those over 16 being more a professional conduct issue.

The initial investigation covered 1975 to 1986, although detectives cannot be sure the offending stopped then.

While there is no evidence of further offences after then, Det Sgt Kenyon admitted officers cannot be certain that none were committed.

"That's why we have left the door open for people to come forward. If they do, we would start a fresh investigation. Everyone deserves justice. We would not treat any complaint any differently just because he has been convicted," he said.