Former drug addicts could be the key to solving a brutal murder in Oxford which has remained unsolved for four years.

Brian Francis, 51, was found beaten to death, with multiple injuries, at his ground-floor flat in Knights Road, Blackbird Leys.

Four years after his murder at the hands of a killer who has yet to face justice, police have renewed an appeal for information, following an inquest held at Oxford Coroner's Court earier this month, which ruled Mr Francis had been unlawfully killed.

Mr Francis was found in his flat, which was well-known as a haunt of drug users, in February 2002, after a mystery telephone caller alerted paramedics.

He had suffered numerous injuries and was pronounced dead at the scene.

A telephone box in Merlin Road, thought to have been used by the person who called 999, was removed by police for forensic tests.

Det Sgt Kevin McGuire, who is responsible for the case, has made a fresh appeal for information which could help him to track down the murderer. He hopes that reformed and recovering drug addicts may have vital clues.

He said: "This was a horrific and frenzied attack and this murder investigation is far from closed. The unlawful killing verdict given by the coroner will continue to be pursued.

"We had a very strong suspect, who was arrested straight after the death, as part of an in-depth investigation into the killing."

The police inquiry was hampered because many of the key witnesses were drug users and were suspicious of the police.

Det Sgt McGuire said: "It's because of this that I make a fresh appeal to those who may have known Brian Francis, or have been involved in such circles.

"It may be that, four years on, these people are in better circumstances and will feel more comfortable about speaking to police about information that could help our investigation.

"No matter how small or insignificant, it could help solve a brutal murder.

"This investigation will continue and anyone with information will be treated with the utmost confidentiality."

Two men, aged 37 and 45, were arrested separately on suspicion of the murder in the week after Mr Francis was found dead. Both were later released without charge.

Det Sgt McGuire said: "Brian's house was known to be used by drug users. Many of Brian's close friends were extremely helpful to the investigation. However, there are some who frequented his address who might have felt unable to speak at the time."

Anyone with information on the case should call Det Sgt McGuire on 08458 505505.