A teenager who allegedly stabbed a friend's father over a drug dealing turf war that escalated in a McDonald's fast food restaurant, told a court it could not have been him because he had become "afraid of knives".

Libyan national Basel Elmaarfi, 19, of Ullswater Crescent, Kingston Vale, denied causing grievous bodily harm to 40-year-old Alexander Danabalan, who was found with stab wounds to his back and leg in Sussex Road, New Malden on the evening of March 30 this year.

Appearing in Kingston Crown Court yesterday Mr Elmaarfi told jurors he had a lot to lose having been on licence for a knife crime from July 2013, and on bail for an immigration offence at the time of the stabbing.

He said: "There is a lot to lose when you go to prison and your mum comes to visit you and she is crying.

"When I finally came out on licence and on bail I was an immigration case. I will die back home because of political problems.

"As soon as I came out of jail I put my hands on the Quran and said I would never do this again.

"I am afraid of knives now."

The former Chessington Community College schoolboy admitted being a previous drug user and having an involvement in drug dealing, but claimed Mr Danabalan's 16-year-old son, Brandon, had phoned him on the morning of the attack and threatened his sister and mother.

He said they had also argued about a drug dealer, known only as Appie, who was a friend of Mr Elmaarfi.

The pair, along with several of their friends and Mr Danabalan met in McDonald's, and after a verbal spat in the New Malden High Street branch, a street brawl allegedly ensued round the corner in Sussex Road that evening.

Mr Elmaarfi admitted getting into a fist fight with Mr Danabalan, but said he ran away before anyone was stabbed having realised he would get into trouble if he became caught up in it.

Prosecutor Tom Nicholson said: "The truth is you got into a fight. Perhaps you were losing, not doing your best, so you took a knife out."

Mr Elmaarfi replied: "I didnt stab the guy. That is what I'm telling you. I had too much to lose."

The trial continues.