Michael Douglas has warned actors against romancing their co-stars after admitting his secret affair with Kathleen Turner.

The 82-year-old actor revealed in his memoir, One Helluva Ride, that the pair fell head over heels for each other when they shot the 1984 adventure-comedy film Romancing the Stone in Mexico while he was separated from his then-wife, Diandra Luker.

And while speaking about his book at London's Royal Festival Hall on October 28, Michael advised budding actors not to make the same "mistake".

According to the Daily Mail, he said: "A lot of actors make the mistake early in their career of having a relationship with their leading lady.

"What they forget is that you can break up. They're having to perform these love scenes, and they hate each other.

"We've all made that mistake, and I try to warn people."

In an extract from One Helluva Ride, shared by PEOPLE magazine, the two-time Oscar winner admitted that he and Kathleen lied about the truth of their love affair for the last 40 years.

He wrote: "The chemistry I had with Kathleen Turner was so strong, audiences have been certain for years that we were in a relationship together while making the film.

"We both denied it through Romancing the Stone, Jewel of the Nile, War of the Roses, and even while doing press a few years ago for The Kominsky Method.

"The official story went as follows: Yes, we confessed, we had amazing chemistry. Yes, we were both, as Kathleen said, 'terrible flirts,' and yes, we were both tempted, but nothing ever happened between us.

"That was a lie."

The Basic Instinct star explained that the lie was "meant to protect my wife and son", Cameron, and they "told the world for 40 years".

He continued: "Kathleen and I never hit a rough spot. We found each other first as friends, then as co-stars, and finally as lovers.

"Following an exhausting day of shooting in the jungle, we'd go out and have a meal, or head out with the group and afterward I would sneak into her hotel room after everybody was asleep.

"There were no cameras in elevators, no assistants using cell phones to take pictures."

They did not tell any of their castmates or director Robert Zemeckis, now 75, but the "magic spell of the set" was broken when his wife and their son Cameron came to visit the set in Mexico and she "grew suspicious".

Michael has recalled how Diandra told Kathleen that they were "still married" as she saw their separation differently.

He added: "After that visit, Kathleen and I ended things, and I went back to Diandra. I did it for Cameron, but we shouldn't have gotten back together. After that first split it was never the same between us ever again."

As Michael referenced, Kathleen, who also appeared with him in the likes of The War of the Roses and The Jewel of the Nile, kept up their public story as she claimed she had "hope for" something romantic between them at one point.

She told Closer magazine: "I was yearning, but he was still married to [to his first wife Diandra Luker]... although they were separated, and so I thought there was hope for me."

After the extract was published, Kathleen, 72, responded to the revelation.

She told People: "Good heavens, what a fuss about something 40 years ago!

"I love Michael, and I look forward to enjoying the book."