The divorce trial of estranged spouses Christie Brinkley and Peter Cook commenced this week and dirty laundry is already airing on a clothesline: Cook has confessed all, Brinkley says she was heartbroken and the drama continues.

The world is well aware by now that former model Christie Brinkley’s fourth marriage has come to a sad end, after estranged husband Peter Cook, a Hamptons architect, had an affair a couple of years ago with his remarkably younger assistant.

Taking the stand Thursday in a Long Island, NY courtroom, the 54-year-old Brinkley confessed that the day she learned of her husband’s affair with his teenage assistant was “the day my world was completely shattered.”

Visibly emotional, the former supermodel recounted the day she learned of her husband’s infidelity, after she had spoken at a Southampton High School graduation in June 2006.

It was then that the stepfather of her husband’s mistress tapped her on the shoulder to say that Cook would not leave his then 18-year-old daughter alone.

The stepfather, Southampton Village police officer Brian Platt, said Cook “won’t knock it off. He’s having an affair with my teenage daughter,” as quoted by People.com.

Platt testified the same on Wednesday.

The former Sports Illustrated model continued to say it was then that she realized there was truth in Platt’s words. Feeling her knees weaken and her vision blur, she searched for a chair to sit on and steady herself.

Cook initially denied his affair with the young Diana Bianchi but there was no denial on his part Wednesday, as he testified that he gave her expensive gifts and tried to buy her silence.

He also confessed to spending thousands of dollars on online porn.

Brinkley, 54, and Cook, 49, wed in 1996. They have a 9-year-old daughter, Sailor; Cook has also adopted the former model’s 12-year-old son, Jack, from her marriage to Richard Taubman. She also has a 22-year-old daughter, Alexa Ray Joel, from her marriage to Billy Joel.

The trial will focus not so much on financial issues – they had a prenuptial agreement – as on the custody of their children.

Brinkley filed for divorce 10 years into their marriage after Cook’s affair with Bianchi became a tabloid scandal.