Tiananmen Square anniversary: Search for last prisoner
3 June 2014 Last updated at 07:57 BST
Twenty-five years ago, Tiananmen Square in central Beijing was the scene of pro-democracy demonstrations.
Crowds of protesters, including students and factory workers, had been camped out in the square for weeks before Chinese security services made their move on 4 June 1989.
Estimates of the death toll range from several hundred to several thousand and 1,600 others were arrested.
The majority of those have since been released but one man, Miao Deshun, a Beijing factory worker, is thought to remain in prison.
Celia Hatton spoke to some of the handful of people who still remember Tiananmen's last prisoner.