Hong Kong–United Kingdom relations a deeply important role in the formation of the modern Hong Kong. Sovereignty of Hong Kong was ceded to the UK "in perpetuity" on 29 August 1842 through the Treaty of Nanking. The UK further expanded the territory of Hong Kong in 1860 by another cessation, plus a 99-year lease of the New Territories in 1898. The stability, security, and predictability of British law and government enabled Hong Kong to flourish as a centre for international trade. Localisation of teritary institutions, the Hong Kong government and the independent Judiciary in the run-up to the 1997 Handover of sovereignty, caused a
British Hong Kong franchise to include them. The Sino-British Joint Declaration was signed by both the Prime Minister of the United Kingdom and the Premier of the People's Republic of China on 19 December 1984 in Beijing. The Declaration entered into force with the exchange of instruments of ratification on 27 May 1985 and was registered by the People's Republic of China and United Kingdom governments at the United Nations on 12 June 1985. In the Joint Declaration, the People's Republic of China Government stated that it had decided to resume the exercise of sovereignty over Hong Kong (including Hong Kong Island, Kowloon,