Because Britain had a 99 year lease on the New Territories of Hong Kong, and this was due to be returned to the Chinese by 1997. The UK didn't have to handover Hong Kong island, but if it didn't then it would have lost too many facilities such as places of work and airports to China for it to function as its own city, and so it was handed back on the condition that it would be a democracy for 50 years.
Prior to 1997, Hong Kong was a British territory.
It is Hong Kong
United Kingdom in 1997
Hong Kong is not a capital of any country. It is part of China.
The United Kingdom
The transfer of sovereignty of Hong Kong from the United Kingdom to the People's Republic of China occurred on July 1, 1997 at the Hong Kong Convention and Exhibition Centre in Wan Chai, Hong Kong.
On the 1st July 1997, the sovereignty of Hong Kong was transferred from the United Kingdom to the People's Republic of China.
After defeating China in a war, the United Kingdom (Great Britain) demanded China give up Hong Kong as part of the Treaty of Nanking
The transfer of sovereignity over Hong Kong from the United Kingdom to the People's Republic of China.
United Kingdom
Hong Kong was previously a British colony, so the mother country of Hong Kong is the United Kingdom. In 1997, Hong Kong was handed back to China under the "one country, two systems" arrangement.
Not until 1997. From 1841 to 1997 it was a Colony of the United Kingdom.