Robert Downey Jr has said prison was "the most dangerous place" he's ever been after he spent a year behind bars amid his drug addiction.
The 58-year-old actor was just six years old when he took drugs for the first time, which turned out to be the first step on his path to addiction and prison.
From 1996 through to 2001, the Marvel star was arrested a number of times on charges relating to drugs such as cocaine, heroin, and marijuana.
In 1997, he missed a court-ordered drug test and spent six months behind bars.
Two years later, Robert missed another test and was arrested again. He was sentenced to three years in prison and ended up spending a year behind bars after being granted early release.
The Hollywood star has said prison was "the most dangerous place I've ever been in my life" and compared it to a "really bad neighbourhood".
Speaking to Dax Shepard and Monica Padman on their Armchair Expert podcast, Robert said he was initially held with a mixture of prisoners.
"Arguably the most dangerous place I've ever been in my life because nobody is designated if they're a level 1, 2, 3, or 4 criminal," he revealed.
Speaking about his time behind bars, he said: "There was no opportunity there; it was only threats: yes, everyone is going to take your wallet so watch it."
Robert was later transferred to the California Substance Abuse Treatment Facility and State Prison.
He said one memorable moment was "walking onto the yard that you're going to be doing more than a year on for the first time.
"The closest thing I can associate it to is to being sent to a distant planet where there's no way home until the planets align."
The actor said he was able to adjust to prison life within two weeks and focused on learning how to get by on a day-to-day basis.
"The most important thing is, as long as you have the willingness to do harm, it is unlikely you will be targeted," he explained.
"It really is that thing of, what is the difference between acting like your willing to do harm and actually being willing to do harm."
Robert added: "I remember the extreme example, and whoever said this is an idiot, they go, 'Always have a plan to kill whoever you meet,' which is probably one of those safety experts who was like a black ops guy."
The special guest was asked by host Dax how he managed to make friends in prison, but Robert replied: "You don't have friends in the joint. You have acquaintances."
He explained how he would sometimes use a handball court to strike up conversation with his fellow inmates.
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