The 14-year-old was stabbed in the stomach on Sunday evening, as bystanders pleaded with the attacker to stop, according to a witness.
The boy was taken to hospital by helicopter after the incident in Islington, which saw two men and what appeared to be two teenagers fighting.
A few minutes into the fight, witnesses said a third teenager ran in carrying the weapon.
Resident Amina Taylor said she saw the stabbing from her flat.
We could all see the knife in his hand. It was that big, she said.
You could hear the screams of ‘No, stop it, don’t do anything, don’t be stupid’ and he went for (one of the adults) first but then he was kind of swinging wildly and then he just thrust the knife into the stomach of the teenager.
She said she was shocked to see somebody who is clearly barely taller than my nine-year-old son coming down with a weapon in his hand.
She described the big and cumbersome weapon as gleaming.
Two boys, 14 and 15, have been arrested in the early hours of Monday on suspicion of attempted murder.
An 11-year-old boy who was also arrested on suspicion of attempted murder has since been released and police say he is no longer a suspect.
The Met Police said that officers retain an open mind as to motive.
They appealed for anyone who saw the stabbing to contact them.
Mayor of London Sadiq Khan said Incidents like this have a devastating impact on families and our communities and we need to send the message that they will not be tolerated.
Politicians, the police and all Londoners must unite in saying it is never acceptable to carry a knife – and it does not make you safer.
News Source SkyNews