The detective heading a 34-year-old murder hunt was once fingerprinted in connection with the case.

Detective Inspector Bill Warner was one of thousands of school children checked at the time 12-year-old Keith Lyon was stabbed to death.

As Sussex Police yesterday announced a £10,000 reward to catch the killer, Mr Warner said: "I was 13 at the time and I remember clearly when I was fingerprinted. Police visited all schools in the Brighton area.

"I had to go to the science class at Dorothy Stringer with my mates to meet plain-clothed police officers."

Mr Warner could never have guessed that more than three decades later he would be in charge of the same investigation.

He said: "My ambition at the time was to play water polo for Great Britain, which I achieved. I never thought of becoming a police officer."

A father himself, Mr Warner, said: "Any murder is tragic but when the victim is a child it is even more catastrophic.

"I remember well how Keith's death at the time was the talking point everywhere you went in Brighton.

"The investigation was enormous and I don't think there was anyone in the town who wasn't aware of it.

"No stone was left unturned by the police then but they did not have the technical and forensic advantages we enjoy today.

"We could employ them now but unfortunately we do not have much to go on."

Mr Warner is banking on pricking consciences and he is confident someone wants to talk.

Keith Lyon, son of the late band leader Ken Lyon, was murdered on downland in Brighton in 1967 as he walked from his home in Ovingdean to buy school equipment in shops at Woodingdean.

Several people have called Brighton CID since Keith's 82-year-old mother, Valda, made an emotional plea in The Argus.

Officers are checking new information but they are still waiting for the breakthrough they need. They do not need to hear from people who think they know those responsible. They need concrete evidence.

Mr Warner is convinced the killer or killers still live locally and that others, who the culprits have spoken to, are holding back.

He said: "How people can keep a terrible secret like this I simply don't know. I know I could not do it.

"This has devastated the Lyon family and they continue to suffer. Those responsible must be suffering too and may have psychological problems.

"What happened that Saturday affected a great number of people and it is still affectin them 34 years later."

Mr Warner is desperate to solve the case, primarily for Keith's family.

The man in charge of the original investigation, retired Detective Chief Superintendent Jim Marshall, who solved a record 100 murders in his career, could not bring Keith's killers to justice, but he is still hopeful.

He admitted: "I get very sad. This has lived with me and rankled me from that day to this but I am still hoping it will be solved.

"People still stop me in the street and ask me about the case."

At a recent press conference he pleaded "in the strongest possible" way for people to come forward and help the police.

He gestured towards Mrs Lyon, sat next to him: "Please, allow this lady some peace of mind."

Anyone with information should contact Brighton CID on 0845 6070 999.