"It made me realise I was Chinese, confronting an authoritarian regime face-to- face, in the hands of the National Security Bureau. It was my first experience of fear."
Mr Lee was the only Hong Kong person to be arrested during the 1989 democracy uprising. He had intended to deliver HK$2m (pounds 170,000) to the demonstrators, but was taking the money back to Hong Kong because the situation had become too chaotic. "They confiscated the money," he recalls. "I still have the receipt."
While Mr Lee was being questioned and threatened in Peking for three days - as a warning, he believes, for Hong Kong not to get involved in Chinese affairs - a million people marched through the then British colony to commemorate the dead of Tiananmen.
Mr Lee's interrogators sent him home after forcing him to sign a confession admitting to undefined wrongdoing. He has not been allowed to return to the Chinese mainland since.
If the idea was to frighten Mr Lee off, it backfired. As soon as he returned to Hong Kong he began helping activists to get out of China and took part in the effort "to break the news blockade by the Chinese authorities". Leaflets and videos, smuggled over the border, reached a vast audience.
Today he will be among the leaders of a protest march demanding democracy in China and on Friday, the 10th anniversary of Tiananmen, he will be on the platform of the candle-lit annual commemoration rally, which still attracts a bigger turnout than any other political event in Hong Kong.
"People have not forgotten what happened," he says. "June the fourth changed many people in Hong Kong: they will not easily discard this memory."