Margaret Thatcher, the late British prime minister, once praised Deng Xiaoping’s famous “one country, two systems” formula for Hong Kong as an “ingenious idea” that elegantly grafted the capitalist British colony back on to Communist China.

In the years immediately after Hong Kong returned to China’s fold as a “special administrative region”, its civil freedoms and capitalist economy were safeguarded. But almost two decades after the 1997 “handover”, the former Chinese leader’s apparently simple solution has become a source of misunderstanding and conflict.

The Chinese government and Hong Kong’s pro-democracy camp are locked in a bitter fight over fundamentally different visions for the territory’s political future. One emphasises Beijing’s ultimate authority while the other stresses the sanctity of Hong Kong’s “second system”.