A teenager accused of the “angry and vengeful” murder of Lewis Blackman last February claims he “lost self-control” and “stabbed out” at the Kentish Town man after being stabbed himself, having a precious necklace stolen and then being “taunted”.

Barrister Mr James Wood QC told the jury in closing arguments on Thursday morning that the defendant, a 17-year-old who cannot be named because of his age, had been left “distressed” by a “brutal and violent robbery” at a late-night birthday party.

The prosecution disputes this. Mr Tom Little QC told the jury it was “simply incredible” to be asked to believe the defendant’s story of having lost self-control.

He told the jury: “This is a group chase. It is a group attack and it’s about revenge. He didn’t lose self-control when he was stabbed, or when his mobile phone was taken.”

Mr Blackman, 19, was a former student of Acland Burghley School in Kentish Town. With a group of friends he attended a 16-year-old girl’s birthday party in Earl’s Court before being, the prosecution argued, chased from the premises and stabbed 14 times.

Summarising the case for the jury. Judge Anthony Leonard QC said: “The prosecution argue he was stabbed by the defendant both when he was running and when he was on the ground.

“The defendant’s case is when he left the flat he was intending to leave the area but when he heard someone shouting he decided to go after Blackman to recover what had been taken from him

“The defence say Lewis Blackman taunted him, saying ‘come and get it’ and ‘I’ll shiv you all up’ and it was at this point that the defendant lost it.”

The prosecution talked the jury through CCTV which shows Mr Blackman, sometimes known as Dotz or Dotty, racing away from what Mr Little described as a “wild pack of teenagers”, before he received a stab wound to the back from a boy the defendant acknowledges was him.

Mr Wood said the teenager deserved credit for coming before the court: “He has not only come here, but he has admitted stabbing out.”

The defence argue that the defendant did not even know if he had connected with Mr Blackman when he swung the knife.

The trial continues.