CENTRAL ISLIP, New York – Christie Brinkley's estranged husband said Wednesday at the start of their divorce trial that he had sex with his teenage lover in his office, then paid her $300,000 while hoping to keep their affair quiet.
Peter Cook, 49, called to the stand by his wife's divorce lawyers, was questioned about his affair with Diana Bianchi, who testified Wednesday that she had a "mutual" affair with Cook that began when she was 18, shortly after he hired her for his Hamptons architectural firm.
"We had been working together and he had shown interest in me and I reciprocated," she said.
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Bianchi said Cook asked her how she would feel if he told her he was attracted to her.
"I was taken aback but wasn't against it either, but I didn't really respond," she said. Bianchi also said Cook asked her to lie about the affair, and that she did lie about it.
Earlier, the fashion model's lawyer said Cook spent about $3,000 a month on pornographic Web sites.
"That is the man who's come before this court and asked for custody of his 13-year-old son and 10-year-old daughter," attorney Robert Stephan Cohen said. The couple's daughter, Sailor, had her birthday on Wednesday.
Cook's lawyer, Norman Sheresky, said of the porn allegation that Cook had acknowledged it. "It was wrong and he said it was wrong," Sheresky said.
In opening statements at state Supreme Court in Central Islip, in Long Island, N.Y., Brinkley's lawyers accused Cook of adultery and cruel and inhuman treatment, and said that Cook trolled sex Web sites for swingers, checked out an escort service and other dating services and used a Webcam to broadcast himself masturbating in cyberspace.
In November 2006, their son Jack accidentally opened a porn slideshow of young girls on Cook's computer, Brinkley's lawyers said.
But the main focus of the trial is Cook's affair with the 18-year-old, which set off a frenzy in the tabloids. Cohen said Brinkley, 54, found out about it from the teenager's stepfather; the fashion model got the bad news moments before she was to speak at the Southampton High School graduation.
Brinkley's team said that Cook denied the affair at first when she confronted him, then said "I only kissed her," then said "She took off her clothes in my office one Saturday and she said more or less 'Let's have sex' — what's a guy to do?"
Cook's lawyer said Brinkley is partly to blame for the public spectacle.
"For goodness sake: She's on her fourth husband," Sheresky told the court. "Your honor, we're here because of the self-indulgent wrath of a woman scorned."
Cook said he met Bianchi in early 2005 when she was working at a Hamptons toy store. Their affair began that March, around the time he hired Bianchi. She was paid $20,000 to type magazine articles onto the company's Web site. He also left her cash payments in various spots: $500 under the rock outside his office; more behind a painting.
Before their relationship ended in late 2005, they had sex in the office a number of times, and at homes in the Hamptons owned by Brinkley.
Bianchi got the $300,000 in May 2007. The exact purpose of the money was not specified, but Cook said he was trying to protect himself and his family from scandal.
Cohen said Brinkley paid for everything throughout the marriage as Cook "quickly transformed himself as a person to the manor born." But custody, rather than money, is the couple's main dispute. Brinkley's ownership of her $30 million Bridgehampton home is not being contested.
Cohen said Brinkley is a doting mother whose work schedule revolves around her children. Her ex-husband, pop singer Billy Joel, is also involved in their lives.
"Uncle Billy is around to support these kids," said Cohen.
Alexa Ray Joel, 22, the daughter of Brinkley and Joel, was called to testify about Cook's "constant criticism of Alexa," said Cohen.
Joel testified that Cook treated her well before he married her mother. But she said he was constantly on her case afterward, chastising her "if I chewed too loud" and criticizing her piano playing.
"He was just very critical of me in general," said Joel, a singer, songwriter and pianist.
When her lengthy shower caused a leak in the kitchen below in 2003, Cook stormed into the bathroom and demanded she mop up immediately, Joel testified. When she got downstairs wearing only a towel, he pushed her head into a bucket and yelled, "You clean this up!" she said.
When Brinkley found out, "she was horrified," her daughter said.
Sheresky said there's ample evidence that Cook's a good parent, including interviews in which Brinkley referred to him as "the best dad in the world."
The lawyer quoted Brinkley as saying: "Peter is our rock. He's the calm in the middle of the storm."
Earlier this week, Sheresky told FOX News entertainment correspondent Jill Dobson that it is "terrible, almost inexcusable" to want press at a custody or divorce trial when there are children involved.
Cohen shot back that Cook shouldn't have done anything that he's ashamed of.
Asked by reporters if he'd marry again, Cook said Wednesday that he "never thought I'd get divorced."
FOX News' Jill Dobson and Kathleen Foster and the Associated Press contributed to this report.