In November 2011, Zhang Guangde received an urgent summons to a factory town in southern China where his son, Tingzhen, was working for Foxconn, the Taiwanese contract electronics manufacturer for Apple and one of China’s biggest employers.

Tingzhen, a 28-year-old migrant worker from central China, had been on a ladder, fixing a security light, when he suffered an electric shock, fell about four metres and struck his head on the ground. By the time Mr Zhang arrived at his son’s bedside in Shenzhen, a manufacturing centre in Guangdong province, doctors had removed a portion of his dangerously swollen brain. Tingzhen, once a champion track and field athlete, was bedridden for more than two years and has only recently begun to walk again. He will require care for the rest of his life.

Tingzhen’s accident set his father on a four-year odyssey through every tier of China’s justice system — the courts, arbitration and, when those two avenues failed, a centuries-old petitioning system through which peasants once appealed to imperial authorities for redress.