Detectives investigating the murder of a man in a busy high street have put out an appeal for a man on a bike - seen on CCTV when the attack took place - who could be a key witness.

Lamarni Hylton-Reid of Warwick Grove, Clapton, was found suffering from a stab wound at around 5pm on Wednesday August 21 in Homerton High Street at the junction with Kenworthy Road.

The 20-year old, who was described as “one in a million” by friends, was taken to hospital but pronounced dead just over an hour later.

Messages paying tribute to Mr Hylton-Reid, from Clapton, flooded on to social networking site Twitter, including one post which said he was stabbed in the chest on his way to visit his mother on her birthday.

Detectives have stressed the man on the bike is not a suspect, but could turn out to be a vital witness in the investigation.

He was seen riding a black mountain bike past the scene of the attack on the corner of Roding Road and Homerton High Street, and is believed to have been knocked off the bike during the fight.

He also entered a local food shop to ask for an ambulance to be called.

He is described as a black man, aged about 30 to 40, with a clean shaven head and was wearing a white vest and white shirt with black trousers.

A teenager appeared in court on August 28 charged with stabbing Hylton-Reid to death in a busy high street, following a row over a £5 note.

The 17-year-old boy from Clapton, who cannot be named for legal reasons, was charged with his murder and appeared at the Old Bailey via video link from Warren Hill Young Offenders Institution in Suffolk.

He has also been charged with threatening a person with a sharply pointed article, and is due to appear at the Old Bailey on 13 November.

A 19-year-old arrested for assisting an offender has been bailed pending further investigation.

Det Sgt Danny Perkins, from the Homicide and Major Crime Command (HMCC), said: “We are very interested in speaking to this witness and ask that he contacts us in confidence on 020 8345 3865 or call Crimestoppers anonymously on 0800 555 111.”