Provided you are not seen by the government as disruptive, being a Christian is not difficult in China today. If you do step over that line, defined by the constitution as making use of religion "to engage in activities that disrupt public order", the consequences can be harsh. The authorities believe in exemplary punishment, what a Chinese proverb calls "killing the chicken to frighten the monkeys" and, having identified a target, pursue it ferociously.

For example, the Shouwang Church in Beijing, the largest of the unregistered Protestant groups in the city, has been hounded by the police over the past two years. Having been locked out of property it had either rented or bought, its congregation has been forced to hold services in the open air. Members have been arrested, evicted from their homes and jobs or deported to the towns from which they came. Gao Zhisheng, a Christian human rights lawyer, currently imprisoned in north-west China, has been in and out of detention since 2006. After one of his releases, he said he had been tortured and threatened with death if he spoke about what had happened.

Ma Daqin, the Auxiliary Bishop of Shanghai, has not been seen in public since last July, when he declared at his consecration that he was leaving the Chinese Catholic Patriotic Association to devote more time to the pastoral needs of the diocese. The CCPA and its associated Bishops' Conference of the Catholic Church in China promptly withdrew recognition from him. The gravity of this case is that Ma's appointment was approved by both the Chinese government and the Holy See, part of a slow rapprochement between the two sides which has now suffered a severe setback. Reversing it will be one of the toughest diplomatic challenges facing Pope Francis I.

The life of Jin Luxian, the 96-year-old Bishop of Shanghai, provides a fascinating insight into the Vatican's attitude towards China under Popes John Paul II and Benedict XVI. A Jesuit, Jin spent 27 years (1955-82) under house arrest, in re-education camps or in prison for being part of a "counter-revolutionary clique". The devastating experience of the Cultural Revolution convinced him that the interests of Chinese Catholics were best served by co-operating with the government, so he became the CCPA-appointed bishop of China's most populous city in 1988. The bishop approved by the Vatican, Ignatius Kung Pin-mei, who had been consecrated in 1950, found himself powerless in his own diocese after being freed on parole from a life sentence in 1985. He left to receive medical treatment in the United States and never returned. In 1979 John Paul II had secretly created him a cardinal.

However, the same pope tacitly approved the presence of papal representatives at Jin's consecration as auxiliary bishop in 1985, and his successor, Benedict XVI, invited him to attend a synod in Rome in 2005, only to have the Chinese government turn down the invitation on his behalf.