Stephen Searle, 64, denies the murder of his 62-year-old wife Anne Searle and is on trial at Ipswich Crown Court.
Andrew Jackson, prosecuting, said Searle "probably" used a choke hold learned while serving as a Royal Marine to strangle her after a row at their home in The Brickfields, Stowmarket, Suffolk on December 30 last year.
In a 999 call played to the court on Monday, Searle told police: "I've just killed my wife".
Asked how he killed her, he said: "Suffocation really. Bit of a bizarre situation, but never mind."
The call handler asks: "Are there just the two of you in the house?"
"Well, just the one of us now," he replies.
In the call made at 10.19pm, Searle said it happened "about an hour ago" and added he had considered going to sleep and calling police in the morning.
Mr Jackson said: "The prosecution say that his delay in reporting the killing and his consideration of further delay was to allow him time to concoct an explanation to hide the truth."
Searle, who says he was acting in self-defence, gave an account to police that his wife came at him with a knife causing a wound to his hand and three pinprick marks to his stomach.
In a prepared statement, Searle told officers: "I was in fear for my life and during the struggle this terrible accident happened."
A post-mortem examination recorded the medical cause of death as compression of the neck, noting that external bruising suggested the application of a hand or the crook of an elbow in a choke hold.
It said Mrs Searle would have lost consciousness after about eight to 15 seconds of pressure being applied to her neck.
"Death, however, required further sustained pressure on her neck for a period of minutes," said Mr Jackson.
Searle, who has three sons with his wife of 45 years, had had an affair with the partner of his son Gary, the court heard.
Anastasia Pomiateeva, 39, giving evidence from behind a screen, said she had children with Gary.
She said she first met Searle while he was a manager at the bowling alley where she worked in 2005, and she began a relationship with his son Gary around 2010.
She said that last year the former Ukip councillor invited her to the Suffolk County Council offices for a drink and she went with her one-year-old son.
"He showed me all round the place," said Ms Pomiateeva. "He was very proud to show me where he worked."
She said she went to Searle's office and he "asked me if I was happy with Gary and if I was getting enough sex" and then "said he wasn't happy and he wasn't getting any from Anne".
She said Searle would send her photos of him bodybuilding.
She showed Gary and he said "don't worry, dad's just drunk", she said, adding that Searle later sent her a photo of a sausage on a plate.
Ms Pomiateeva said she later had a sexual relationship with Searle.
He gave her the nickname SBG, Steve's Beautiful Girl and called his wife a "piece of s***", she said.
"He used to call me that too when I didn't please him," she said.
"He used to say it was the drink but he used to call me some nasty names as well."
She said the Searle family "loved their alcohol", adding: "The whole family, they drink like fish. Like I would drink water, they would drink beer."
Searle lost his seat as Suffolk county councillor in the May elections last year.