A WEALTHY businessman told a jury he “turned into a monster” when he stabbed his partner to death in an explosion of rage.

John Butler said he feared Pauline Butler, the mother of their three sons, was about to attack him because she had pulled a knife on him three times before.

When she put out her hand to grasp a large kitchen knife on the table next to her, he thought she was going to use it against him.

Butler, 62, the boss of Kettley’s Furniture Centre in Yeadon, denies murdering Mrs Butler at her flat in Cherry Lea Court, Rawdon, on April 14.

But he told Leeds Crown Court yesterday he admitted he was “criminally responsible for her injuries”.

Butler, of Larkfield Road, Rawdon, said he had always loved his partner of almost 40 years.

Although they had never married everybody thought that they had wed and she had changed her name to his.

Butler, wearing a dark suit, wept in the witness box when he told the jury: "I always loved Pauline, right from the beginning. She had a lovely face, a lovely profile. We were just the perfect couple.”

He added: “I just wanted her to be happy. She could have had anything.”

In 2004 the family was hit by a “bombshell” when Mrs Butler was diagnosed with breast cancer. She became depressed, was not showing him any affection and there were frequent arguments.

She moved out of the family home about five weeks before her death.

Butler said she had pulled a knife on him three times.

On one occasion she gestured towards him with a weapon before saying: “You’re not really worth it, are you?”

The day before Mrs Butler’s death, Mr Butler said he felt a “wreck”. He was not sleeping and he was drinking too much.

On the morning of April 14 he called at the flat to mend a microwave, but Mrs Butler was angry to see him and flew into a rage.

It was when she said their weekly trips out with their grandchild would have to end that he exploded.

“It was devastating. That is my life gone, isn’t it?” he told the court.

He grabbed the knife as Mrs Butler swore at him and ordered him out of her home.

“It was an explosion. It was like two hundred thousand volts running through your body. It was like an alien took over your mind. I turned into a monster,” he said.

He told the jury it was a Jekyll and Hyde moment.

“She was rising up from the chair and grabbing and clawing and I just remember my hand swinging over,” he said.

He recalled swinging the knife twice before Mrs Butler stood up and pushed him back into the centre of the room.

He tripped into a small table and she fell onto her back with him on top of her - the knife was in her chest.

“It was like waking up from a blackout,” he said.

It was over in seconds and he had no recollection of how she received any other injuries, the court heard.

He said he took the knife and went into the bathroom, adding that he never intended to kill, or seriously injure, his partner.

The trial continues.