There were shouts of "stab him, finish him off" before a Thornton Heath teenager was stabbed to death on New Year's Eve, a coroner has heard.

Kyall Parnell, 17, was stabbed at around 10.40pm in Norwood Road, Tulse Hill, on New Year's Eve after his friends confronted another group who they had chased off the number 68 bus.

A coroner has now heard how Kyall had been urged by by his friends to kill his attacker.

Detective Inspector Ian Titterrell, from the Metropolitan Police's Homicide and Major Crime Command, told Southwark Coroner's Court that Kyall was stabbed as he confronted a 16-year-old boy.

Mr Titterrell said "there were words to the effect of 'stab him, finish him off'," which the younger boy later told police caused him to fear for his safety and take out a knife from his bag before plunging it into the victim.

The 16-year-old, who was arrested and bailed, also told police he had been stabbed before in attacks involving Kyall.

Mr Titterrell said the 17-year-old had been seen acting "very aggressively" towards one member of the group that boarded the bus shortly after him and his friends.

"As those three males walked up to the top deck where Kyall and his friends were sitting, there was immediately a confrontation," he said.

"The three males who had just got on at Tulse Hill got off the bus and they were pursued by Kyall and his friends, with two of the males seeking refuge in a convenience store.

"Witnesses had seen the chasing group in possession of knives and Kyall is seen in very clear CCTV on the route 68 bus to approach an individual in a very aggressive manner with his hand placed towards his left hip area - there was a suggestion of something glinting.

"A knife was found on Kyall afterwards.

"The male, fearing for his safety, has stabbed Kyall once in the chest. This stab wound pierced the heart and it's that that led to his death."

Mr Titterrell said the investigation was ongoing but at this stage the Crown Prosecution Service had indicated that it would not charge the 16-year-old attacker with a homicide offence because of the "real issue" of self-defence.