Dad Steven Stiles told a jury yesterday of the horrifying moment he saw Karl Quincey cut Barry Cooper’s throat.

Mr Stiles, 44, was giving evidence at Winchester Crown Court. Quincey, 33, of Longcroft Avenue, Devizes, has pleaded not guilty to murdering Mr Cooper, 28, of Eastleigh Road, Devizes.

The court heard Quincey was at Mr Stiles’s ground floor flat in Victoria Road when Barry Cooper arrived at about 4.30pm last June 27.

Mr Stiles, who has 11 children, said he was in the doorway of his flat and Barry Cooper was in the passageway when, without warning, Quincey came out.

Mr Stiles said: “Karl grabbed hold of Barry, pulled his head back and cut his throat in front of me. He flung him down to the floor and all I could hear was a punching sound. I thought he was hitting him in the face. Barry was on his back. Karl had Barry’s legs up by his shoulders and was stabbing him in the neck.”

Mr Stiles said the knife was a double-bladed silver dagger about 5 to 6ins long. He added: “Barry was just begging him to stop but Karl said nothing at all.

“He wasn’t a human being. It was Jekyll and Hyde. I have seen nothing like it, he was a man possessed. It was the most sickening thing I have ever seen in my life. My mind was saying to help Barry, but my legs and body wouldn’t let me go.”

He said after the attack Quincey looked at him and shrugged his shoulders with a big smile on his face. Then Quincey stamped on Mr Cooper’s head. “It sounded like the bones breaking, it will be a noise I will never forget,” he said.

Mr Stiles said Quincey wiped the knife on his combat trousers and put it back in the sheath on his belt.

Mr Stiles and neighbour Hannah Diskett put Mr Cooper in the recovery position and Mr Stiles called 999.

Mr Cooper was flown by air ambulance to Great Western Hospital, Swindon but died the next day.

The prosecution say Mr Cooper was stabbed at least eight times in the neck.

Before the attack Mr Stiles saw Quincey in the Market Place and said he was angry with Mr Cooper because he said Quincey was responsible for a burglary at neighbour Jimmy Waite’s flat.

The court heard Mr Stiles had lied to police when he was first interviewed. He told detectives he did not see Mr Cooper being stabbed and had opened his door to find a man on the floor and spatters of blood.

He said: “At that time I knew Karl wasn’t arrested. I was worried not only for myself but for my family and children.”

Mr Cooper’s father, Michael, was present in the public gallery.

The trial continues.