Seven teenagers were questioned by police yesterday after a 16-year-old boy was chased by a mob and stabbed to death in a London street lined with £1 million homes.The murder is the fifth involving black youths in London in the past few weeks.Witnesses say that teenage girls egged on the attack with shouts of “Kill him, kill him” before the victim, named last night as Kodjo Yenga, was surrounded. At one point Kodjo raised his arms to fend off blows from sticks. The suspects being held include four 13-year-olds, two 15-years-olds and a man aged 21.Last night police sources said that Kodjo had been a “nice lad” and a promising A-level student who had never been in trouble with the police. His family live in North Kensington close to Ladbroke Grove. He was a student at St Charles Catholic Sixth Form College in North Kensington, West London.The attack took place in Hammersmith Grove, West London, at teatime on Wednesday on the edge of a quiet residential area known as Brackenbury Village.The street links Shepherds Bush to Hammersmith Broadway and would have been busy with pedestrians and traffic. Residents include the broadcasters John Humphrys and Jeremy Vine. The actor Ralph Fiennes lives 100 yards from the murder scene.One witness, Tom Grimes, 42, said: “There were about 15 black youths hanging around by the shops. There were girls and boys aged 15 or 16 wearing school blazers. They were getting very rowdy and the girls especially were shouting aggressively.”