A murder trial at the Central Criminal Court has heard details of a letter sent to the victim, Jean Gilbert, by the man with whom she was having an affair.
The court heard that David Bourke of Laverna Dale, Castleknock in Dublin, who denies murdering his wife, found the letters and knew his wife was going to leave him.
He told gardaí the thought of seeing her with another man sent him 'into a rage'.
Mr Bourke cried in court as the letters from his wife's UK-based lover were read to the court.
In one letter, Robert Campion declares his love for Jean Gilbert and said not marrying her in the past was the biggest mistake of his life.
The court heard that Mr Campion had known Ms Gilbert since 1986.
They had re-kindled a relationship in 2007 after meeting occasionally throughout the intervening years at Buddhist conferences.
Mr Campion told gardaí that he had moved to Ireland in August 2007 to be with Ms Gilbert and was staying in a hotel.
On 28 August, the morning she died, Ms Gilbert had come to visit him at the hotel at about 5.30am but returned home later that morning.
In statements to gardaí, Mr Bourke said on the day he stabbed her, Ms Gilbert had left the house in the early hours of the morning and had sent him a text to say she had a message to do.
He had sent her a text to say 'we both know you don't have any message to do'. He said she returned home and looked so smug and self-satisfied.
Mr Bourke said the fact that she looked so 'smug, self-satisfied and content' contributed to his decision to stab her. He said he was trying to cause her serious harm but not enough to kill her.
He said he was not in his right mind at the time.
Mr Bourke told gardaí he had been feeling angry, hurt, betrayed, abandoned and lonely after his wife announced that she was going to leave him.
She had also asked him to leave the house but he said he had no intention of leaving. He had begged his wife to re-consider but she had refused, he said.
'The thought of seeing her with another man sent me into a rage,' he said.