The father of a boy with terminal brain cancer told police he flipped after he thought a man had hit his pregnant wife and children in the street.

John Banks was stabbed in the chest and arm after he stopped to rebuke children who had nearly knocked him off his bike.

Mr Banks, 51, told a jury yesterday at Hove Crown Court one of the teenage boys spat at him and threatened him.

It is alleged he was stabbed by Jason Murray after a confrontation between the two men outside his house on August 29.

Murray, 26, of Southall Avenue, Brighton, denies intentionally causing Mr Banks grievous bodily harm and claims he acted in self-defence.

PC Peter Tatton said Murray approached him as soon as he arrived at the scene and told him he had done it. He told the court: "He said, it is me. I did it.

"My boy has got cancer and I am really upset. This guy was hitting my kids and pushing my wife over. It all happened so fast. I did not mean to hurt him."

Murray was arrested and when interviewed said he had been preparing a meal when his wife Dale shouted a man was hitting children in the street.

Murray said he was a head chef who had given up his job to care for his son who was having chemotherapy at a hospital in Liverpool.

During the interview he said: "My son is four and has got cancer of the brain and spine and my wife had gone upstairs to check him.

"She shouted that there was a man outside fighting with kids and my seven-year-old son Anthony was out there."

He said he went out of the house still holding the kitchen knife he had been cutting up food with.

Murray told officers Mr Banks had gone towards him aggressively pointing a finger and shouting at him. He had returned to the house to put on some shoes when he heard his son shouting Mr Banks had pushed his wife over.

Murray said he went back outside again and Mr Banks advanced agressively towards him. He told officers he "flicked" the knife towards Mr Banks to warn him to back off. He said: "When I realised what had happened I was sick. I was in bits. He was pushing my wife and I just wanted to scare him.

Mr Banks suffered a punctured lung and spent 16 days in hospital recovering from his injuries. The trial continues.