In extracts from her new autobiography Love, Lipstick And Lies, Katie - aka Jordan - says she caught her then boyfriend Danny having sex with a woman he picked up at a party.
In the book which is serialised today in the Sun On Sunday, Katie reveals how she had suspicions her younger lover was cheating so decided to head round his house...
Katie, now 35, goes on to describe the moment she walked into his bedroom in 2011 and caught him cheating on her.
She writes: "My gut instinct had been spot on, Danny, who was supposed to be my boyfriend, was having sex with another woman."
The revelation explains why Katie calls the rugby player 'Danny Chipolata' and why she publicly warned Kelly Brook about him when the model went on to date him.
Katie is now married to Kieran Hayler, the father of her fourth child Jett Riviera, who was born in August.
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