Peter Cook detailed his affair with his former assistant that led to his divorce from Christie Brinkley on the first day of their divorce trial, US reports.

Peter Cook details his affair with Diana Bianchi

Cook, 49, recalled how he frequently had sex with Diana Bianchi, then 18, in his office and at homes owned by Brinkley.

Brinkley's attorney — who said Cook spent $3,000-a-month on web porn — said that the model, 54, found out about the affair from the teen's stepfather before she was to speak at a high school graduation.

"Peter has apologized," Cook's lawyer shot back. "He's cried his eyes out. He's lost his marriage."

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