The downfall of Shenzhen Mayor Xu Zongheng has sparked a guessing game among gossip-mongers about the identity of the 'mysterious' actress implicated in the case. Days after news broke that Xu was put under shuanggui - a form of discipline under which the Communist Party detains officials under investigation - reports began to emerge that the lavish lifestyle of an actress had put Xu on the graft-busters' radar. The actress has not been named, but clues about her identity tantalise those interested in political and celebrity gossip. She was said to have obtained a Hong Kong identity card recently under the Admission Scheme for Mainland Talents and Professionals and has allegedly alerted the security authorities with her frequent trips between Hong Kong and Shenzhen. Another clue circulating on the Web is that she is from Hunan province, Xu's home province, and that she had helped set up an interview for him on CCTV. This helped to narrow down the possibilities. It has been a tradition for mainland media and websites to engage in gossip about mistresses when a corruption case surfaces. Weeks ago, Guangdong law and order tsar Chen Shaoji, who was being investigated for graft, was said to have kept a Guangdong television news anchor as his mistress. The golden rule is that behind every corrupt official, there is one or more young and beautiful mistresses who help with money laundering and networking. According to a survey by the mainland's top prosecutor's office in 2007, 90 per cent of the country's most senior officials sacked for corruption charges in recent years had kept mistresses. The link between women and corruption is obvious, but why do mistresses become a talking point only after an official is brought down for corruption, but not when the official is still in office? It is an open secret that mainland graft probes are always a result of party infighting. Exposing a rival's immoral conduct is the most convenient weapon for political foes. A typical example was when former state statistics chief Qiu Xiaohua was jailed for bigamy. Many asked why other officials with mistresses were not charged. But the most outrageous case in recent years would be Li Wei, a mistress shared by former finance minister Jin Renqing, former Sinopec chairman Chen Tonghai and Qingdao party boss Du Shicheng.