Kenneth Bae is an American missionary to North Korea and organises groups of people visiting North Korea to pray: "they took it as a great threat, they said that I was trying to overthrow the government by prayer and worship." He was arrested and sentenced to 15 years hard labour.
He was on 5 live's afternoon edition yesterday, follow this link from 1 hour 10 minutes in. Bae has just published a book on his experiences. "We had a lot of conversation (with the guards in the labour camp).. they started wondering about why I believe, once they said 'you are the prisoner, we are the guard, why do you seem happier than us, where does your joy and hope come from?.... you are a very strange kind of prisoner, you are always singing, always praying.' "
Well worth a listen, grim insight into a very dark place.