Two men arrested in connection with the murder of a 12-year-old schoolboy 39 years ago are no longer being treated as suspects, police said today.

A 55-year-old from Manchester and a 56-year-old from Brighton were held in July on suspicion of the murder of Keith Lyon.

Today, Sussex Police disclosed they have been "stood down" from bail and are no longer considered suspects in Keith's murder.

"The police investigation is still active and inquiries are ongoing," a police spokesman said.

Keith was repeatedly stabbed on a bridle path in an area known as Happy Valley, between the villages of Ovingdean and Woodingdean, near Brighton in 1967.

One of the biggest murder investigations ever mounted by Sussex Police was launched in the wake of the murder.

The inquiry led to more than 80,000 home visits being made and more than 6,000 fingerprints of local schoolboys taken.

Although there were a number of suspects, no-one has ever been charged in connection with the case.

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

To the embarrassment of police, the murder weapon was lost until workmen discovered it again four years ago in a sealed room at Brighton's John Street police station.

Keith's father, Kenneth, died in 1991 and his mother, Valda, died in October 2005, having failed to see justice done for their son's murder.