Last year the photographer Haohui Liu revisited a single roll of negatives left behind by his late grandfather, Zhangming Chen, a professor of geology in Daqing, a city of three million in China’s far northeastern province of Heilongjiang. Daqing occupies a special place in post-war Chinese history. In 1959, oil was discovered in the area. Engineers and technicians such as Zhangming were dispatched to the city to manage the production boom that followed. Many spent the rest of their lives there. In Daqing’s harsh winters, the countryfolk who came to the city for work wore heavy padded clothes similar to prisoners. There are stories of the local police confusing them for runaway convicts when they returned home. In the 1960s, the Western powers, led by the United States, enforced an energy embargo on Mao’s China, an act of aggression compounded by the Sino–Soviet split, when the Kremlin also restricted supplies to the country. Faced with spiraling scarcity – Beijing buses in the period were converted to run off natural gas packs due to the lack of petrol – the ramped-up production of oil at Daqing made the city a savior of the revolution. ‘In Industry, Learn from Daqing’ runs one of Mao’s injunctions from the period. The city’s name, which was given to mark the tenth anniversary of the People’s Republic, means ‘Great Celebration’.