Christopher Landau explores the explosive growth of christianity in China, with millions flocking to the official Protestant and Catholic churches. The country has the world's largest bible printing press while some factories are run on Christian principles. Why has the Communist state, which is formally atheist, endorsed this transition? There is official interest in the idea of a "Protestant work ethic" aiding the country's economy while some branches of government hope that the church's social services will help care for an ageing population. Producer: Caroline Finnigan.