A jazz saxophonist warned his married lover to watch her controlling husband's "every move" the day before she was knifed to death in their study in Newcastle, a court has heard.
IT consultant Mark Arthur, 50, denies murdering his wife Heather but admits her manslaughter on the grounds of loss of control, Newcastle Crown Court has heard.
The privately-educated former British Airways manager was in the throes of leaving her partner of 30 years, whom she met at Kingston University, when he stabbed her in the chest at their home in Gosforth last April.
Mrs Arthur had by then fallen in love with saxophonist Paul Gowland, 44, who played in a number of different groups, including the band Strictly Smokin', which she watched in local pubs.
The day before she was killed, Mrs Arthur, who was 50 and raised on the Isle of Wight, told her secret lover the couple were going on a final day trip out to the National Trust home, Wallington Hall.
Mr Gowland urged her to go somewhere with plenty of people around, texting her: "Please watch his every move, honey. You have to be careful."
She replied: "I promise I will keep in view of others."
Mr Gowland told the jury he was worried about her safety.
"I was concerned about what might happen, given the defendant's history," he said.
Asked to explain, he replied: "Just violent exchanges and unpredictability.
"She said she walked on egg shells all the time and was afraid."
Mark Giuliani, prosecuting, asked: "Why did you understand Heather wanted to separate from her husband?"
The musician replied: "She had years of unhappiness, felt intimidated, felt threatened in some way, didn't have any freedom in her life, he was always tailing her, interrogating her. He was unaffectionate towards her."
The jury has heard Arthur, who would spend hours alone working at their home in Woodbine Avenue, had installed GPS software on her phone so he could track her movements.
He headbutted her car so hard it caused a dent to the bodywork during one row about them splitting up, the court has heard.
Mr Gowland agreed with Joanna Greenberg QC, defending, that Arthur did not know about his wife's affair.
"Her husband didn't know about her relationship with you, and that was the position throughout," she said.
"Correct," the saxophonist replied.
Dressed in boxer shorts, Arthur went to his GP and burst in on an appointment to say he had badly hurt his wife.
Dr Sarah Taylor had seen the defendant a week previously as he was concerned he had cancer and Asperger's syndrome, the court heard.
He was due to see her for a follow-up appointment on the day he barged in, the doctor said.
Dr Taylor told the jury: "I was in the middle of my consultation and suddenly the door opened and Mr Arthur was standing in the doorway. I didn't recognise him at first, he was standing there in his boxer shorts.
"He was saying something that I couldn't clearly hear.
"I got up from my seat and went up to him and asked what he was saying. He told me that he had hurt Heather, he had badly hurt Heather, I needed to help Heather."
An ambulance was called to their home and police arrived at the surgery, the court heard.
The week before, he had appeared very anxious and scored 21 out of 27 on a psychological test, indicating moderate depression.
She referred Arthur to a mental health practitioner for further treatment, she said.
The trial continues.