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 nationality law and Hong Kong on or after 1983 to a parent settled in Hong Kong are BDTCs. The law also stated that British Citizens or BDTCs by descent could not automatically pass on British nationality to a child born outside the United Kingdom or the dependent territories concerned unless a parent acquired citizenship otherwise than by descent. Negotiation concerning the future of Hong Kong started in the late 1970s between Britain and China. With the signing of the Sino-British Joint Declaration on 19 December 1984, the future of Hong Kong was set, with China to assume sovereignty of the entire territory of Hong Kong