As the killers were led away, one wagged his finger at jury members and relatives shouted abuse from the public gallery. Judge Geoffrey Grigson told the jury not to take any notice, but two women members were close to tears.
The three convicted - David Huggins, 18, Aaron Cole, 19, and James Pearce, 19 - will be sentenced on 22 October. Steven Plank, 18, and the juvenile were cleared. None of the five, who denied the charge, gave evidence in the six-week trial.
Emotions had been running high in the "close-knit" London community, with complaints over a "wall of silence" encountered by police.
Jamie Robe, 17, died from complications after suffering 20 injuries including broken ribs, skull fractures and facial damage. He was set upon after being sick on the pavement near the Osprey estate. He became involved in an argument with two youths and at least six others joined the attack.
Some trial witnesses had their identity protected. One witness, Traci Broughton, 19, said she had been rehoused and placed in a witness protection programme.
She saw the attack and told the court a sixth youth, who was not on trial, stamped on the teenager's head several times to "make sure he was dead". The noise was like the "cracking of knuckles", she said. This youth cannot be named for legal reasons and he is still wanted.
But Jonathan Goldberg QC, lead barrister for the defence and representing Cole, accused Ms Broughton of being an attention-seeker. Jamie's father, Stuart Robe, who persuaded witnesses to come forward, said after the trial: "I am very pleased with the verdict and now I plan to get on with my life and start living properly. I feel real hatred towards the murderers. They have destroyed me and taken my son's life. Nothing they get can ever restore my son."
The Liberal Democrat MP Simon Hughes had acted as an "honest broker" for witnesses.
Mr Goldberg suggested the MP was "conned" by two Turkish witnesses. He said the men had "haggled" to get permanent immigration status for the older man and a business loan, with the help of Mr Hughes. "Mr Simon Hughes, God bless him, must have been putty in the hands of those two," he said.Reuse content