A teenager accused of knifing his sister's lodger to death in a row over the state of her flat told police he was scared the victim would kill her, a court heard.

Jahangir Hussain, 18, left 27-year-old Fijian Robert Venenavuci with fatal injuries after plunging a kitchen knife into his chest and stomach.

The pair had clashed just weeks after the victim and his girlfriend Kallati Dhurgha moved into the spare room of a flat owned by Hussain's sister Halima Khatun.

Relations between the couple and their landlady began to sour when Miss Khatun complained that they had not been keeping the apartment clean enough, the court heard.

Prosecutors say that following an explosive row on the night of October 4 last year, Hussain, of College Road, Isleworth, grabbed an 8in kitchen knife and stabbed the unarmed victim twice, once in the stomach and once in the heart.

He denies a charge of murder.

The Old Bailey heard that when he was arrested, Hussain insisted he had acted in self defence after Mr Venenavuci punched him and started throttling his sister.

Detective Sergeant Justin Howick read a transcript of the defendant's post-arrest interview to the court.

During the interrogation, Hussain said he visited his sister's flat with two of his nieces to bake cakes and watch TV.

He said the family had just finished watching X Factor and were on the sofa Little Britain USA when Mr Venenavuci came into the room.

"He was standing around being rude and asking stupid questions", the defendant told officers.

"He was pointing to me saying: 'Who's he? What's he doing there?'

"It looked like he was poking her [my sister]. He kept on asking: 'Who's this? Who's this?'"

The defendant said Mr Venenavuci appeared drunk, and spoke so close to his sister's face that he was spitting on her.

He said the two siblings went to the kitchen to wash up, but were followed by the victim.

Hussain told officers: "He made a swing at my face and hit me there. I staggered back. He grabbed my sister around the neck.

"He was throwing punches at me.

"He said something like 'knife', then he started to move towards the kitchen knife.

"As I was closer I just grabbed it straight away.

"I tried to punch him but it was the knife that hit him on the face.

"I said to him: 'Let go, get out', and not to hurt my sister, and all this time we were shouting: 'Call police, call police', to my niece.

"We shouted really loud: "Help us, help us.

"He was throwing punches at me, hitting me in the chest.

"And then I lunged forward a few times.

"He fell to the floor. I just dropped the knife."

Hussain said he heard his sister shouting: "He's going to kill us."

He added that when he first saw Mr Venenavuci that night, he did not know who he was and had no idea he was a tenant.

The trial continues.