Fear of being stabbed led one man to knock another man “sparko”, a court has heard.

St Albans Crown Court heard on Friday that Stephen Lowe punched Andrew Boag because he was being “attacked” and thought he would be stabbed.

Mr Boag died following an incident on Friday, July 25, 2008. Lowe has pleaded not guilty to murder.

Lowe told the court he and Mr Boag, who had known each other for around 20 years, saw “eye to eye” until he encouraged Tereasina Leighton to report Mr Boag to the police after he assaulted her.

“People were telling her not to go through with it because he would stab her,” he told the court. “I said: 'He's not your brother, your father, your husband. No man has got the right to do that.”

Then when Mr Boag was released from prison in June 2008, the court heard Lowe received a telephone call from him.

“I got a call saying: 'You're a grass, I'm going to kill you.' I laughed and called him a Nokia gangster,” he said.

When asked why he didn't report the threats made against him to the police, Lowe told the court: “There's no point. Andy was untouchable. He could do as he pleased. He's stabbed people, cut people, hurt people, he never got anything.”

Ms Leighton was also targeted with threatening phone calls, the court heard, when Mr Boag would call Lowe a grass and tell her: “He's going to get it”.

Lowe, who is known as Frosty, told the court he was aware of Mr Boag's “reputation” and said he saw Mr Boag pull out a knife on several occasions, notably when drug deals went wrong.

He said: “He was knife happy. A couple of people used to call him the surgeon because he's cut that many people.

“My reputation is a gentle giant. Someone said I was like marmite, you love me or you hate me. I try to be a humble person.”

Lowe identified a knuckle-duster found inside the Mercedes taxi at the scene in Garsmouth Way, Watford, as one belonging to Mr Boag, and said he believed Mr Boag also carried a gun on one occasion.

The defendant told the court that he had been working away from Watford to “keep away from” Mr Boag, but returned to the town to see Ms Leighton, to give his son a teddy bear and get his washing done, on Friday, July 25.

He said: “I had no plans to see Andy. No-one told me he would be there.”

But the court heard that when he got out of a white transit van in Garsmouth Way, he heard Mr Boag shout: “Frosty, you f****** *****, you're going to get it.”

The jury heard that Mr Boag leaned into a waiting taxi's open passenger door and stood up with his right hand behind his back.

Lowe said: “I knew that's where Andy carries his knife. I've seen it too many times. I know him, I know his character, that's his way. I'm not turning my back on Andy if he's got a blade.”

The defendant said he “shortened the ground” between himself and Mr Boag, before grabbing his right elbow with his left hand. Lowe was then put into a headlock under Mr Boag's left arm, the court heard.

“I tried to hit him two or three times in the side so he can release me,” he told the jury.

The men then fell into the passenger seat of the car, and as they continued to struggle against each other, Lowe put on a knuckle-duster he had found at a fair several days earlier, the jury heard.

“I put my hand in my back pocket to where I had the knuckle-duster. I just wanted to stop what was going on. I was still being attacked by him,” he said.

Lowe told the court he then heard a woman on the back seat tell the taxi driver: “Pass it to me or give it to me”, referring to Mr Boag's knife.

The court heard Lowe was on top of Mr Boag, punching him while Mr Boag was “throwing his arms about”, as the pair ended up in the middle of the front seats, with Mr Boag's head on the rear seat.

Lowe said he then knocked Mr Boag “out cold”, as it was the only way he was sure he wouldn't be stabbed by Mr Boag.

He walked away from the scene toward the waiting transit van. He told the court, however, that he turned back to the car and saw a young woman he described as “hysterical”.

He said: “I looked at him [Mr Boag] laying on the back seat. There was blood by his nose and mouth and air bubbles coming from his nose. I could see him breathing. I thought he was alive.

“I said to Jason [the taxi driver]: 'When he wakes up, that's a boyslap. Leave the f*** alone'.”

Asked by Ann Cotcher, QC, why he punched Mr Boag, Lowe told the court: “He was still attacking me. I knew if I didn't knock him out I would have got stabbed.”

Lowe told the court he “couldn't believe it” when he was told Mr Boag had died.

He said: “He wasn't dead when I left him and I was shocked. He was somebody I knew. I didn't mean to seriously hurt Andy. I just tried to stop the attack.”

In court, Lowe admitted cannabis and crack cocaine use – the latter he described as a “performance enhancing bedroom drug”.

The defendant, who was involved in four semi-professional boxing fights from 1997 to 2004, also spoke about how he saved a man's life in 1993.

He was walking along a bridge where he met a man about to commit suicide, the court heard.

Lowe said: “I walked across and took ten minutes out of my life and spoke to him. He started to cry, we hugged and I walked off.”

The man didn't kill himself and, following an appeal for the “suicide hero” in the September 9, 1993 edition of the Watford Observer, Lowe received an award from Hertfordshire Constabulary, the court heard.

Stephen Lowe, of Breakspeare Close, Watford, has pleaded not guilty to murder. He has also pleaded not guilty to an alternative count of manslaughter.

The trial continues.