How a brick wall in Beijing became a beacon for those calling for change. But when Wei Jingsheng posted an essay demanding democracy in 1978, he was arrested and imprisoned for 18 years. He's been telling Rebecca Kesby why he thinks it was worth it.

(PHOTO: BEIJING, CHINA: China's prominent dissident Wei Jingsheng (R) laughs as he talks to reporters at his Beijing apartment 20 September 1993. Wei was arrested again shortly after this and eventually released from prison on medical grounds in 1997. He currently lives in the USA. (credit MANUEL CENETA/AFP via Getty Images)