British Prime Minister Margaret Thatcher shakes hands with Chinese Premier Zhao Ziyang after signing the Sino-British Joint Declaration on December 19, 1984.

The secret negotiations that sealed Hong Kong's future

Updated 0652 GMT (1452 HKT) June 22, 2017

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Hong Kong (CNN)The two leaders sat several feet apart at a long table covered in green silk.

Between them, a tiny twin flagpole bore the standards of the United Kingdom and the People's Republic of China.