The 17-year-old boy, who cannot be legally named, stabbed 23-year-old John Temitope Onetufo in Grove Street on December 31 at 12.35pm.
Today (January 7) the teenager appeared at the Old Bailey charged with his murder.
The court heard that the victim was lying in the middle of the street after emergency services were called just before 12.30pm.
He was pronounced dead at 1.10pm.
Before the stabbing, it was alleged the defendant had been arguing with Mr Onetufo amid an ongoing dispute.
A post-mortem examination found Mr Onetufo had suffered a stab wound to the chest which was up to 18cm deep and had penetrated his heart.
The defendant appeared before Judge Mark Dennis KC by video-link from Feltham young offender institution.
The judge set a plea hearing for March 26 and a provisional trial from September 14.
The youth was remanded into custody.
