Police have arrested two men on suspicion of a boy's murder 39 years ago.

Schoolboy Keith Lyon was 12 when he was stabbed repeatedly with a serrated steak knife after going for a walk on downland between Woodingdean and Ovingdean, near Brighton.

As part of the original investigation, 80,000 home visits were made and the fingerprints of more than 5,000 schoolboys were taken - but no one has ever been charged.

Sussex Police are now hoping for a breakthrough following the arrests of a 56-year-old man from Brighton and a 55-year-old man living in Manchester on Thursday. Police only released details of the arrests today.

Both men have been released on police bail until November 14.

It was on May 6, 1967, that Keith left the family home in Ovingdean, Brighton, to buy a geometry set.

He was walking across the downland to shops at Woodingdean when he was attacked and stabbed 11 times in the chest, back and abdomen.

The blood-stained murder knife was found near a wall. Close by in toilets was evidence of someone having washed blood from their hands and clothes.

Keith's body was found by a teenage girl on a grass bank near Warren Road at about 4.15pm.

One theory is that Keith was picked on by young yobs because of the way he was dressed. He was a smart boy and a pupil at Brighton and Hove Grammar School. He was wearing part of his uniform at the time.

The attack sparked one of the biggest murder investigations ever seen in Sussex.

It has been the subject of a number of reviews over the years and was reinvestigated on BBC's Crimewatch in 2000 and 2001.

Detective Inspector Tim Nunn, the senior investigating officer, said the latest arrests were part of the ongoing investigation.

He said: "It is one of a number of lines of enquiry we are continuing to pursue and these will continue over the next few months.

"Clearly there have been many appeals for information over the years but we are still interested in hearing from people who, for whatever reason, have felt unable to disclose it previously.

"I believe there are people who know who committed this murder but have not had the confidence to speak to the police about it. Now is the time to do so, so that Keith's remaining family can finally understand what happened that tragic day in 1967."

Police are particularly interested in hearing from anyone who can help identify a family with a teenage son who emigrated to Canada shortly after the murder. A number of witnesses have mentioned this family but none has come up with a name.

The murder weapon was lost by police for decades.

Workmen found the knife four years ago after coming across a sealed room at Brighton police station in John Street. On the weapon were two types of blood: the victim's and possibly the killer's.

At the time detectives hoped modern DNA and forensic tests would identify whose blood it was.

Keith's band leader father Ken Lyon died in 1991 and his mother Valda died in October last year.

Mrs Lyon's desire was to get justice and she gave a number of pleas for information in The Argus and on Crimewatch.

Keith's musician brother Peter, who was seven at the time, said his life has been overshadowed by the murder.

He said: "I have had to live my life not knowing why my brother died but knowing that the person or people who murdered him are living their life without being punished for Keith's death. If you know who killed Keith, please share your secret with the police."

Anyone with information should call Sussex Police on 0845 6070999 or Crimestoppers anonymously on 0800 555111.