A businessman said he stabbed his wife after his “whole world just collapsed in a second” when she told him she was having an affair.
Arthur said the revelation his partner of 30 years, Heather Arthur, was leaving him for another man “was just too much for me”.
The 50-year-old has admitted the manslaughter of his wife but denies murder on the grounds of loss of control.
He said he was already worried about going to the doctors to be tested for cancer that day and claimed his wife had verbally abused him at their Gosforth home one morning last April.
Arthur said: “She launched into this tirade which got very personal, very quickly. She started saying that I was manipulative and controlling, that I never showed her any affection.
“I asked her why she was saying these things. That’s when she turned to me and said that she was having an affair.
“I had never heard that before and never suspected that before. She said she was going to leave me and seek a divorce.”
Describing his reaction, he added: “I could not understand why somebody I loved this much was attacking me so viciously.
“The shock of all of this coming out in the way that it did just made me very, very angry and the anger came out. My blood pressure went through the roof, my heart was beating so fast I don’t know how I didn’t have a heart attack.
“I developed tunnel vision, everything else went pink. My whole world just collapsed in a second, everything I thought I knew was gone.
“I picked up the knife which must have been right there on the desk. Then I remember both of Heather’s hands wrapped round my hand.
“Then I just remember standing up and pushing forwards. That’s when Heather got stabbed.”
Arthur, who said he didn’t intend to harm her, said he started trying to revive his wife but she didn’t respond.
He said: “I was trying CPR but it was not working. I was panicking, I didn’t know what to do next. When I looked in Heather’s eyes I thought she was dead. I just spiralled into despair.
“My brain was shutting down, I couldn’t believe what had just happened.
“I was not sure if it was real.”
Arthur said he picked up the phone to raise the alarm but thought it would take too long so ran to the nearby Gosforth Memorial Medical Centre to seek help, wearing just his boxer shorts and a top.
Asked how he felt afterwards, Arthur said: “I was in a bad way, I can’t imagine feeling any worse. It’s the worst I have felt by far, I honestly thought I was just going to die at any moment.”
Arthur said he had struggled to remember what had happened when interviewed by police after his arrest. Joanna Greenberg QC, defending, asked: “Did you realise you had been responsible for Heather’s death?”
He replied: “My brain just wouldn’t go there.”
The barrister asked: “Up until Heather confronted you with what you describe as the destruction of your whole life, would you ever have contemplated laying a finger on her?” “No,” he replied.
Mrs Arthur, 50, was planning to leave her husband in the weeks before she was killed after falling in love with saxophonist Paul Gowland, 44.
She died from a single stab wound to the chest, which pierced her heart, at the couple’s home on Woodbine Road, Gosforth, Newcastle.
Arthur admits manslaughter but denies murder.
The trial continues.