The mother of a young man with learning difficulties who was murdered for the sake of his mobile phone has called for an end to "unacceptable" knife crime as her son's teenage killers faced life behind bars.
Dean Mayley, 24, who had a mental age of nine, was stabbed in the heart by Jamal Jones after the gang of knife point muggers surrounded him as he walked home in Greenford, west London on February 7.
The whole incident was caught on graphic CCTV film which provoked gasps from jurors and tearful shock from Mr Mayley's family when it was shown in the trial of the four youths.
An Old Bailey jury took just four hours to find Jones, 17, unanimously guilty of murder, and his three accomplices - Michael Mensah, 18, Ryan Beresford, 19 and Miguel Leiba, 17 - guilty of manslaughter as well as attempted robbery.
Jones had earlier admitted trying to rob Mr Mayley while Mensah was also found guilty of a similar robbery on a 15-year-old boy the month before.
As the verdicts were read out, the youths began wailing and had to be removed from the dock while the judge adjourned sentencing to October 2. Mr Mayley's mother Donna wiped away tears and said "let them cry".
Outside court, supported by her daughter Emma, Mrs Mayley said she was happy with the verdicts but they would not bring her son back.
Calling for an end to knife crime, she said: "They need to be aware when they have a knife or a sword or a Taser they are not going to have fun with these things, they are dangerous weapons.
"It keeps happening day after day, week after week. People will be killed. It is always innocent people who have done nothing wrong. It's completely unacceptable. Things have to change."
Earlier, the trial judge Martyn Zeidman QC lifted a court order allowing the two 17-year-old defendants to be named for the first time, saying : "The more people who realise the horror of knife crime the better."
He added: "Yet another example of a kind and innocent person losing their life because of somebody else using a knife.
"For somebody to lose their life in these circumstances is a disaster. There are no sufficient words to demonstrate the sadness. I want to pay tribute to the family who have shown such courage at difficult times throughout this trial. I just wish there was some way - obviously there isn't - in which I could turn the clock back."
He said the defendants would be in custody for a "very, very, long time" as he ordered reports to assess their risk to the public in the future.
During the trial, the court heard Mr Mayley had caught the eye of the muggers because he was alone and wearing a North Face jacket.
But the 24-year-old had learning difficulties due to a brain disorder called Microcephaly and probably did not fully understand what the teenagers wanted when one of them demanded his phone, the jury was told..
The prosecution said while only Jones, from Acton, west London, wielded the knife, all four played their part in the killing.
Leiba, from Hanwell, and Beresford, of Acton, blocked the victim's path while Mensah, 18, of Greenford, sat in his car parked nearby, waiting to drive them away.
In his defence, Jones denied he had meant to harm Mr Mayley, saying: "He was getting fidgety. His hands were in his pockets. He was looking straight into my eyes. Ryan and Miguel - I noticed them coming back towards me. I asked them 'are you going to get involved?' but they just stood there.
"I asked him again 'just give me your phone'. He shrugged and said 'what are you going to do about it?'.
"And then I just literally panicked. I did not know what to do and I'm thinking 'is this guy going to hit me?' because of his body language.
"I thrust out first. I hit him first - I did not intend to hurt him. I just meant to do a slice and that's it. I just ended up getting paranoid and he was getting aggressive towards me."
He said he had been made to look after the knife earlier in the day by another boy who approached him in college.
But prosecutor Simon Denison QC said all four youths had told a pack of lies about their involvement in the killing.
The jury was shown a menacing letter Mensah wrote to Jones in a bid persuade him not to implicate him in the murder while they were awaiting trial.
He ordered the knifeman not to say that he had given him the murder weapon or that he told him to carry out the attempted robbery.
The letter read: "Why do they think I gave you the nank (knife) and persuaded you? They can't say that without proof."
A search of Jones's bedroom uncovered a kitchen knife stashed under his mattress and a meat cleaver on top of his wardrobe.
The jury was also told about Mensah's previous convictions over the possession of a lock knife, Samurai sword and a five-inch jagged blade which police found when they stopped his car.
What the jury were not told was that in a search of Mensah's bedroom, police also found a Taser.
Following the guilty verdicts, the investigating officer Detective Inspector Mark Lawson said: "I'm absolutely delighted with today's verdicts.
"It sends a clear message that if you are armed with a knife and prepared to use a knife you have got to accept the consequences of your actions.
He added: "We know that these four youths had carried out a number of robberies in the Greenford area before this tragic murder but unfortunately the victims were too scared to come forward."