Hong Kong–United Kingdom relations are the international relations between the post-colonial Hong Kong and the United Kingdom. Hong Kong was a British colony from 1841 to 1941 and again from 1945 to 1997 when sovereignty was handed over to China. UK policy towards Hong Kong is underpinned by its substantial commercial interests, and fulfilling obligation as the other signatory of Sino–British Joint Declaration on the future of Hong Kong, in addition to support Hong Kong's mini-constitution, the Basic Law, and in accordance with China's policy of observing "one country, two systems". Hong Kong is also home to roughly 2.9 million British nationals, 350,000 of which hold an active British passport, giving it one of the largest populations of British passport holders in the world behind only the Anglosphere Commonwealth realms and the United States. History The United Kingdom and the group of offshore islands in the southeastern Pearl River Delta that is today known as Hong Kong have had a long history, playing 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 tertiary institutions, the Hong Kong government and the independent Judiciary in the run-up to the 1997 Handover of sovereignty, caused a progressive retirement of resident British citizens in Hong Kong Civil Service into a minority. Bilateral agreements Articles 151, 153 and 155 of Hong Kong Basic Law permits Hong Kong to conclude non-military bilateral agreements with foreign countries, while articles 152 permits Hong Kong joining international organisations. Both Hong Kong and the UK are full members of FATF and World Trade Organization, and are bilateral participants on air services agreement (since July 1997), Investment Promotion and Protection Agreement (since April 1999), Mutual Legal Assistance Agreement (since 2002), Surrender of Fugitive Offenders and Transfer of Sentenced People Agreements (since March, 1998), and Double Taxation Avoidance Agreement (since 2010). Hong Kong institutions still retain full and associate memberships in Association of Commonwealth Universities and other appropriate organisations under the Commonwealth Foundation umbrella. Political relationships Articles 82 and 92 of Hong