The knife used to kill Adam

This is the first image of the knife detectives believe was used to kill teenager Adam Regis, the nephew of former Olympic sprinter John Regis, exactly a year ago.

The photo of the 20cm blade - which was found one and a half miles from the murder scene - was released today by police as the 15-year-old's family launched a fresh appeal for help in catching his killers.

No one has been charged with Adam's murder despite a £20,000 reward for information leading to a conviction. Police made 14 arrests in the first few months of the investigation but they were later released without charge.

Officers also released an image of the car used by the suspects to flee the scene while Adam lay dying on the pavement in East Ham. The rare bronze Volkswagen Mk II Scirocco will be driven around the area this week on a trailer to jog the memories of potential witnesses.

Adam, a talented sportsman and popular schoolboy, had been to the cinema with his girlfriend and friends on the night he was murdered in an unprovoked attack.

He was stabbed with such force that the knife went through his right arm, into his chest and pierced his aorta. He was found collapsed and was taken to Newham General Hospital where he later died.

Five people are under suspicion for the attack which happened at the junction of Boundary Road and Kingsland Road.

Today's appeal, launched at Upton Park football ground, starts a week-long series of events, including a school presentations and lorries bearing appeal posters touring Newham. A mobile police station will also be placed near the murder scene to act as a focal point.

On Saturday a minute's silence was held in memory of West Ham fan Adam before the side's match against Blackburn. Both teams' players wore black armbands and his sevenyearold brother Dennis Juniorwas a mascot.

Detective Chief Inspector Matthew Horne, from the Homicide and Serious Crime Command, said he wanted to allay the fears of people afraid to come forward and convince them to help. He said: "It's now a year since Adam, an innocent schoolboy, died... We still don't know why he was murdered but we do know that he did nothing to provoke what happened to him that night.

"We still need help to bring the killers to justice and our appeal is particularly to those who may be scared to come forward and talk to us.

"We can help - you can give your evidence from behind a screen and via video link instead of standing in the courtroom, your name won't be said in open court and your voice can be disguised so no one will know who you are."

Anyone with information should contact the incident room on 020 8345 3375 or anonymously on Crimestoppers on 0800 555 111.

A 19-year-old shot in south London has become the ninth teenager to be murdered in London this year. The victim was found by police on Friday evening at the Myatts Field Estate in Stockwell. He was taken to a south London hospital by ambulance but died a few hours later from a gunshot wound to the head.

Scotland Yard said it was keeping an "open mind" about the motive and detectives from the Met's Operation Trident who investigate black-on-black crime, are leading the case. Witnesses are asked to ring 020 8247 4553 or Crimestoppers on 0800 555 111.