Michael Douglas has revealed how everyone "missed" his secret romance with Jeanne Tripplehorn.

The 82-year-old actor has confirmed he had a secret romance while filming Basic Instinct while he was separated from then-wife Diandra Luker, and he recalled that all the speculation about him and Sharon Stone meant no one noticed what was happening with his other co-star.

In his new memoir One Helluva Ride, he wrote: "They were so focused on a possible relationship between Sharon and me, they missed the real relationship happening between me and Jeanne."

Michael noted that the pair "took great paints to hide" their romance "from the cast and crew".

He added: "[We] spent so many hours together, talking, really getting to know each other, enjoying each other's company away from the set and everything else in the world."

Elsewhere in the book, Michael admitted he "fell very hard for Jeanne despite our nearly twenty-year age difference".

He continued: "I was crazy about her. But I was also just self-aware enough to know that the worst thing I could do at that moment after nearly twenty years of marriage was jump right into another serious relationship.

"My relationship with Jeanne lasted through production, then we went our separate ways. But I will always think of her as an amazing actress and a truly terrific woman that I was very fortunate to spend time with."

Meanwhile, Michael has confirmed he made sure Jeanne, 63, was happy for him to reveal their romance in his book, given the time that's passed, and her 26-year marriage to her husband, actor Leland Orser.

He told PEOPLE magazine: "It's been a long time, but I called her up and asked for her permission. That's her business. She said yes."

Michael's fling with Jeanne isn't the only relationship he opened up about in the book.

He also told the story of how he and Kathleen Turner, 72, fell for each other in secret during filming for 1984's Romancing The Stone.

He explained: "I didn't name anybody for the sake of notches on your holster or something like that. These are people that I've had relationships with in my life."

Kathleen has given her thoughts on the matter to the outlet, playing down the big reveal.

She said in a statement: "Good heavens what a fuss about something 40 years ago! I love Michael and I look forward to enjoying the book."