Police say it is unclear how Ben got involved in the disturbance
Four youths have been arrested on suspicion of the murder of 16-year-old Ben Kinsella who was stabbed to death in north London.
Ben was attacked during a row in York Way, Holloway, on Sunday. He died of multiple stab wounds to the torso.
On Tuesday hundreds of people marched to the scene of the killing to protest against escalating knife crime.
Police stopped the traffic as members of Ben's family led the crowd on the march from Islington Town Hall.
The procession was organised by Ben's close friend Brooke Dunford, 16, who sent out leaflets, e-mails and posted messages on a social networking website.
I just couldn't sit around and grieve when this might happen to other people
Brooke Dunford, march organiser
Protestors walked down Upper Street wearing T-shirts with Ben's picture and slogans including "RIP Ben", "You're an Angel", "Stop Knife Violence", "You're Always in Our Hearts" and "18?".
The group paused outside London Mayor Boris Johnson's home on way to York Way.
Ben, who died in hospital hours after the attack, is the 17th teenager to be killed in London this year.
Miss Dunford said: "I just couldn't sit around and grieve when this might happen to other people.
"If by doing this today I have made one person rethink taking out a knife then I have done my bit. That would be one more person going back home to his mum," she said.
The crowd shouted 'no knives' as they marched
A Metropolitan Police spokesman said: "Four males have been arrested on suspicion of the murder of Ben Kinsella and remain in custody at various north and east London police stations at this time."
One youth was arrested on Monday afternoon, two others were arrested later that night and one on Tuesday.
Det Ch Insp John Macdonald said they had had a "good response" to appeals for information about the incident but were still keen to speak to witnesses who may have seen the stabbing or know the identity of the killers.
Detectives are carrying out forensic tests on two knives found close to the scene to ascertain whether the weapons are related to the inquiry.
Officers are also examining CCTV footage from the club and the road where the teenager was stabbed.
Police said the motive for the killing was "unclear" and there was nothing to suggest it was gang related.
On Monday Det Supt Vic Rae said four black youths aged 17 or 18 were believed to be involved in the incident.
He said the row probably began after a group of youths were evicted from the club, but "how Ben got sucked into the disturbance is unclear".
The fight then spilled on to York Way where Ben was stabbed.
Ben, a student at Holloway School in Islington, had completed his GCSE exams and was out celebrating with friends.
One of his friends said Ben made a desperate phone call begging for help minutes before he died.
Paying tribute to her brother Brooke Kinsella, who played Kelly Taylor in the BBC One soap Eastenders, said: "We tragically lost not only a beautiful son and brother, but a true angel.
"Our hearts go out to every family who has also suffered this awful tragedy - and now it truly is the time to stand up and put an end to this.
"Please, please let us learn from Ben and every other child that has been stolen from us," she said.
Two youths arrested over his murder have been released on police bail until a date in late August pending further inquiries.
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