Twenty-one years ago this month Hong Kong was handed over to China after 150 years of British colonial rule. The principle on which China assumed sovereignty of the territory is known as “one country, two systems”, guaranteeing the people of Hong Kong a high degree of autonomy, the rule of law and basic freedoms. The Sino-British Joint Declaration, an international treaty negotiated in 1982 and lodged at the United Nations, gives Britain legal as well as moral responsibility to monitor the protection of Hong Kong’s way of life for 50 years after the handover.