30/05/2009 Shen Tong

Shen Tong was one of the young Chinese student leaders in the Tiananmen Square protests of 1989.
In the bloody aftermath he fled to the United States and became an activist in exile.
Now at the age of 40 he runs a software company in New York and has made a handful of visits back to Beijing.
So how does he look back on those heady events, twenty years on?