Albert Woodfox, America's longest-serving solitary confinement prisoner, has given a harrowing insight into his 43 years inside a six-by-nine-foot cell, describing it as the "most brutal attack on the sanity of a human being".
Woodfox survived more than 15,000 days in isolation in Louisiana's notorious Angola prison for the murder of a prison guard - a crime he insists he never committed - before he was released on his 69th birthday in February.
He was deprived of almost all human contact for many hours a day, the opportunity to watch his children and grandchildren grow up, and the chance to say goodbye to his mother and sister, who both died during his time inside.
In his first British television interview since his release, Woodfox told ITV's On Assignment that his incarceration inside the tiny cell "seemed like an eternity", and described in disturbing detail how he witnessed many of his fellow inmates go insane - and his own personal battle to avoid the same fate.
"It don't get no darker than watching a man go insane in his cell and you fight hard to try and save him and you lose the battle," he said.
"I can't tell you how many men that I formed strong bonds of friendship with go insane.
"Usually it would manifest itself in guys curling up in their bunk in a foetal position and becoming catatonic. Wouldn't talk, wouldn't answer or in some cases, guys would just start screaming and couldn't stop while some would just rattle their bars all day."
Woodfox vowed not to let the conditions beat him, but the years took their toll. He suffered severe panic attacks and and claustrophobic episodes during his time in captivity. He would often wake up in pools of sweat, feeling as if he were being "squeezed to death".
He admits he came close to losing his mind when his mother died and he was banned from attending her funeral.
"It was probably the darkest moment I have experienced - the only time I came close to losing sanity."
Her grave was his first destination upon his release.
"I wanted her to know her son was free and thank her for all the years of support, and never losing faith or stopping loving me."
Woodfox was part of the so-called Angola Three alongside his friends Herman Wallace and Robert King: three black activists who campaigned against racial segregation and the harsh conditions during their long stints in solitary confinement.
Woodfox, already imprisoned for armed robbery, and Wallace, were convicted of the murder of prison guard Brent Miller in 1972, a charge they always denied. Woodfox insists they were framed in revenge for their political activism.
King was released in 2001 while Wallace died of liver cancer just three days after being released in 2013.
Woodfox was finally released in February after agreeing a plea deal following years of legal wranglings.
He entered prison at a time when Richard Nixon was president and the last Apollo mission to the moon was being launched, and has emerged into a world full of technological change and innovation.
"These are the things you used to see on Star Trek - the science fiction of the past has become a reality."
But he is angry at one thing he believes has not changed: racism in America.
"Racism is alive and well," he says, citing the string of deaths of black men at the hands of police.
He believes the rise of Donald Trump is symptomatic of this.
"It always amazes me that these reporters go out their way not to call him [Donald Trump] what he is: a bigot and a racist."
Woodfox says the billionaire has given racism "a mainstream voice and made it ok to be openly racist again".
He says he will be voting for Hillary Clinton on November 8, but admits he views her as "the lesser of two evils".
Woodfox also admits he has found the transition from prison difficult. In the cell, he explains, he only had to defend the front of himself. Now he is having to adjust to feeling comfortable in a crowd.
"It was overwhelming and still at times it's overwhelming. I was thinking earlier today as I got out the taxi...who'd have dreamed? Who'd have thought? At one point these were dreams. Now they are a reality."
Woodfox, who realised a life-long dream to visit Yosemite National Park in California this summer, added: "I'm constantly accumulating first time experiences I never thought would be possible."
The 69-year-old wants to use his newfound freedom to not only make up for lost time with his family, but also to support the Black Lives Matter movement and to fight to end solitary confinement in America, which is still widespread despite the United Nations saying it can amount to torture.
The country needs to realise, he says, that those being held in the tiny cells are "fathers, grandfathers, grandmothers, brothers, sisters, children".
"They haven't come from another planet - they are human beings. It is immoral to treat another human being the way we do...so I'm trying to give a voice to those hidden behind the walls of solitary confinement."
Asked whether he felt he had been given a second chance, Woodfox replied: "Not so much given as earned. I think I've earned the right to be a first-class citizen, to be a member of society.
"Despite America's attempt to destroy me, they failed."
Watch ITV's On Assignment on Tuesday 25th October at 10:40pm.