Following two years of negotiations, UK Prime Minister Margaret Thatcher and Premier of the State Council of the People’s Republic of China Zhao Ziyang sign the Sino-British Joint Declaration. It is agreed that Britain would relinquish control of the New Territories to China following the end of the 99-year lease (1 July 1997). Britain would also relinquish control of Hong Kong Island and the southern part of the Kowloon Peninsula. China declares that following the return to China in 1997, Hong Kong would become a Special Administrative Region under the ‘One country, two systems’ principle, under which the island retained a high degree of autonomy. The intertwining of the Guangdong and HK economies accelerated after the 1984 agreement.