Juan Mendez's first encounter with torture was as a victim, when he spent 18 long months as a political prisoner in his native Argentina. Now, as a UN special rapporteur on torture, he has a victim's eye-view of the suffering inflicted by solitary confinement and by physical mistreatment.
Mendez has made it his life's work to defend human rights, starting off his career as a young lawyer litigating in cases of disappearances in Honduras and massacres in Peru in the 1970s. Speaking to The Huffington Post UK he explained that he grew up during a "violent armed struggle in Argentina". He was a student leader in a small Catholic university, and he wanted to encourage the government to "start embracing the needs of the poor".
He became a criminal lawyer and an activist but in doing so was branded a subversive and the Argentinean military dictatorship arrested him, subjecting him to detention and torture for 18 months.
Amnesty International adopted him as a "Prisoner of Conscience" and after he was expelled from the country in 1977, Mendez sought sanctuary in the United States.
In 1994, he became general counsel of Human Rights Watch, with worldwide duties before advising the UN on how to avoid genocide.
He is very encouraged that the UK "absolutely did the right thing" in holding an inquiry into the torture of detainees during the 'war on terror', he said on his visit over here before setting off for Kyrgistan and Bahrain on fact-finding missions.
But what is Mendez most proud of? "That's easy", he says, "my children have made me so proud, they are very human rights-aware".
"Taking a Stand" by Juan Mendez is published by Palgrave Macmillan, priced £16.99.