Murder accused Stephen Braithwaite said he does not remember stabbing Nilanthan Murddi after he wrestled a knife off him.
Mr Braithwaite, 31, denies murdering the 17-year-old tamil student in a racially provoked attack.
The prosecution allege he had an argument with the teen yelling “Pakis” at his group of friends from the back of a cab on Sumner Road.
They claim he returned to the group, who were drinking and toasting a friend’s birthday, about 20 minutes later to settle the argument.
Mr Braithwaite, a father of four, denies being in a cab and said he was outnumbered by the group of the teen’s friends when walking up Sumner Road in the early hours of the morning on August 16 last year.
He told Snaresbrook Crown Court: "They were saying 'beat him up, f*** him up' all that sort of thing.
"I was pretty scared.”
He said the teens were throwing bottles at him and swinging at his face, one of them came at him with a hammer.
He said “Nilu” swung at him with a dagger in his hand.
"We were about chest to chest and I managed to grab it out of his hand.
"I pushed him away as hard as I could.
"I did not think it [the knife] made contact with him.
"I remember seeing Nilu drop off to the left, I went back and the boys were still coming forward."
He said he put his hands up and said: "What are you doing that for? Why are you doing this?"
The prosecution say he was beckoning the boys and saying "Come and get me."
Mr Braithwaite said he backed away down London Road and the teens went back into Sumner Road.
Christopher Kinch QC prosecuting said: "They were going to look after their friend who was slumped against the blue hoarding, bleeding."
Mr Braithwaite replied he had not noticed any of that.
Mr Kinch said the defendant was "amazingly lucky" to survive the alleged attack by the group of teens without a mark on him.
Mr Braithwaite claims he was hit on the head by one of the flying bottles and had bruises from the encounter.
Mr Kinch said: "Apart from the bottle you have been attacked by a boy with a knife, you have managed to disarm him and got away but all the while there were bottles thrown at you and a group of boys - 10 to 15 you say - threatening you and some were close enough to swing at you, one of those with a hammer."
He said Mr Braithwaite emerged unscathed despite not shouting for help or trying to run away.
He said: "You dealt with the young man who came close to you, you stabbed him didn't you?"
Mr Braithwaite said: "I did not see any blood on me, I did not see any blood on my clothes, I did not see any blood on my hands, I did not think I had stabbed anyone.”
The trial continues.
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