The attack left the victim permanently blind in one eye.
Jaheim Smith-Williams, 18, and of Whites Row, London, Gabriel Burke-Georgiou, 18, and of Poynton Road, London, and a 15-year-old boy who can’t be named for legal reasons pleaded guilty to wounding with intent to cause grievous bodily harm.
The investigation showed the victim and suspects were known to each other and were linked to rival gangs.
All three defendants appeared at London’s Old Bailey on Friday 9 April where a judge sentenced them to a combined 18 years in jail.
Smith-Williams and Burke-Georgiou were both sentenced to six years and nine months imprisonment. The 15-year-old was sentenced to five years and one month imprisonment.
At just after 7pm on Thursday 24 September, the 18-year-old victim was seated with his electric scooter propped up next to him on-board a northbound train service as it departed Northumberland Park railway station in North London.
Smith-Williams and Burke-Georgiou, both aged 17 at the time, approached the victim and Burke-Georgiou started attacking him while Smith-Williams pulled out a Rambo style knife before lunging towards the victim with at least three stabbing motions.
Passengers seated nearby quickly got up and left the carriage to get away from the incident, blocking the then 14-year-old boy from joining the attack.
The 14-year-old then pulled out a long-bladed machete, approached the victim and joined the attack.
The victim was then forced backwards down the carriage as Smith-Williams hit him with the knife several more times leaving the victim on the floor with his hand over his left eye.
As the train pulled into Meridian Water railway station, Smith-Williams, Burke-Georgiou and the 14-year-old disembarked the service and left the station – Burke-Georgiou did so on the victim’s electric scooter.
The victim also managed to leave the service at Meridian Water station and was found collapsed outside a supermarket opposite the station before the ambulance service was called and he was taken to a local hospital.
He suffered stab wounds to the back of his right shoulder and head, a severe injury to his hand and lost his left eye as a result of the attack.
The knives used in the incident were located by BTP officers in the area surrounding Meridian Water station on Friday 25 September.
BTP Detective Constable, Nick Barr, said: “This was a pre-mediated and vicious attack on-board a busy train which left the victim with life-changing injuries.
“It was incredibly distressing for witnessing passengers and I would like to thank those witnesses for assisting our investigation and bringing those responsible to justice.
“Thankfully, incidents like this are rare on the railway, but you can help us by reporting anything or anyone suspicious to us by text on 61016. In an emergency, always call 999.”