Wang's official résumé describes him as being born in Arxan City , in Inner Mongolia Autonomous Region and having "Mongolian nationality". He joined the police force in 1983, and the Communist Party in 1987. He is listed as a graduate of the Chinese People's Public Security University and the Beijing Municipality's Public Security Management Cadres College, and joined the Public Security Department of Liaoning's Tiefa City in 1992.

After his apparent success against organised crime in Chongqing on Bo's behalf, Wang was fêted as a gangbuster by the common people, and took centre stage in public life. This celebrity came despite accusations by lawyers that he extracted confessions through torture and sacrificed due process in the pursuit of the so-called triad groups.

As early as 2009, speculation was rife in Chongqing that some triad bosses had secretly offered a bounty of 6 million yuan (HK$7.3 million) for Wang's assassination. In addition, a local police source said, several police officers secretly harboured grudges against Wang for pushing them to work seven-day weeks from dawn till dusk.

In an apparent attempt to protect himself, the source said, Wang lived on the 15th floor of the Public Security Bureau's main building in Chongqing, and never used a designated police vehicle.

"Wang was an extremely sensitive and meticulously calculating person who was constantly in an alert state," the source said. "It may have been because he was living in fear of reprisals for bringing down dozens, if not hundreds, of triad kingpins and their friends in the municipal police force or the government, including Chongqing's former police chief Wen Qiang ."

Early in March last year, when this reporter met Wang on the sidelines of the National People's Congress in the Great Hall of the People in Beijing, he was keeping a low-profile, avoiding giving interviews and making it clear he was unwilling to be photographed apart from with his superiors or friends.

In May last year, Bo promoted Wang to vice-mayor with responsibility for overseeing security while retaining his role as chief of police. As a result, Wang became seen as a rising political star who some day might play a key role in the national Public Security Ministry, when his mentor Bo assumed the high office to which he had seemed destined. The apparent improvement in law and order under Wang's iron-fisted crackdown had, in turn, boosted Bo's chances of winning a place on the party's all-powerful Politburo Standing Committee, to be decided at the 18th national congress later this year.

At that time no-one could have dreamed of the sudden downfall which would befall the two men. The first official public sign of the downward slide was an announcement on February 2 on the municipal government's information office microblog that Wang had been stripped of his duties as police chief and been reassigned to take care of the city's education and environmental affairs.

Only later did it become clear that events leading to this move began more than two months previously, when, as foreign media had been reporting, it appeared the death in a Chongqing hotel room in mid-November of Neil Heywood, a British businessman and close friend of Bo's family, had deeper implications.

A report carried by the official Xinhua news agency on April 10 shed even more light on the murky story when it reported the outcome of a reopened investigation into Heywood's death in which Gu Kailai , Bo's wife, and Zhang Xiaojun , a Bo family servant, were the prime suspects.

The long-awaited trial of Bo's wife was held at the Hefei Intermediate People's Court in eastern Anhui province in early August. Gu was convicted of murdering Heywood and given a suspended death penalty, while Zhang was jailed for nine years.

According to a Xinhua report last week, Gu told Wang of Heywood's death by poisoning on November 13 and how it had been carried out, and Wang had secretly recorded their conversation. The recording was used as evidence against Gu in her trial.

Wang also assigned his deputy, Guo Weiguo , who was reportedly close to Gu, to look into Heywood's death, without telling Guo he had recorded the incriminating conversation with Gu, the report added.

Guo, along with Li Yang , the head of the city's criminal investigation squad; Wang Pengfei , the former police chief in Chongqing's Yubei district and Wang Zhi , the deputy police chief in Shapingba district, jointly fabricated a version of Heywood's death in which he had died from too much alcohol. Wang agreed to their deception.

The four senior police officers went on trial in Hefei last month on charges of covering up Heywood's murder and got jail terms ranging from five to 11 years.

Wang also had a closed-circuit video tape which showed that Gu was the last person to visit Heywood before he was found dead, Xinhua said. Heywood's remains were cremated on November 18 without any autopsy being undertaken.

According to Xinhua, Wang and Gu fell out when she attempted to destroy the evidence linking her to Heywood's death.

Wang was upset with what Gu had done and was worried the truth may become known, which made Gu lose her trust in himfurther.

In late December, Wang found that four of his aides had been subject to illegal detention, an ominous portent in Chinese political life, in which the investigation of close allies, such as secretaries or drivers, usually means that the politician themself has made powerful enemies.

Wang seems then to have decided that he needed to take steps to protect himself. He reported to Bo in late January that Gu was under suspicion of killing Heywood. In response, Bo became furious and slapped Wang in the face. This was confirmed by Guo, who was at the scene.

Humiliated and angry, the strong-willed and confident police chief decided to reopen the murder investigation on January 29, days before he was reassigned to oversee Chongqing's education and environment portfolio. In addition, another three of Wang's personal aides were placed under investigation.

Realising that he had been put under surveillance, the technology-savvy and politically sensitive Wang reportedly planned his escape by taking sick leave before going to consult a psychologist on February 6. According to foreign reports, Wang deliberately left his mobile phone in the hospital to fool those on his trail, and left with another phone using a new SIM card.

He disguised himself as an old woman and managed to give his followers the slip, before jumping into a car organised for him by Wang Pengfei.

To the later astonishment of millions of people at home and abroad, Wang drove for a couple of hours to Chengdu , in neighbouring Sichuan province where he entered the US consulate on February 6. His flight triggered the country's biggest political scandal in three decades and put an end to Bo's political career.

CRIME AND PUNISHMENT

November 2007
Bo Xilai is appointed Communist Party chief of Chongqing. Wang Lijun, his close ally for many years, becomes friendly with Bo's wife, Gu Kailai, and visits their home frequently. The next June Wang is made director of public security in Chongqing, and in May 2011 he becomes vice-mayor.

November 12, 2011
Wang and Gu discuss how they can frame British businessman Neil Heywood by pinning drugs charges on him. Heywood had maintained close links with Bo's family for more than a decade and helped his son organise his overseas education.

November 13
Heywood dies in a Chongqing hotel after being poisoned by Gu. Officials say he died of alcohol poisoning, but no autopsy results are released.

November 14
Gu tells Wang about the murder, and Wang records the conversation but assures Gu she will not be implicated in the case.

November 17
Wang passes Gu video from a surveillance camera showing that nobody visited Heywood's room after Gu on the night of the murder. Heywood is cremated the next day. In the next month Gu takes it upon herself to cover up the case, detaining some of Wang's assistants, which sours her relations with Wang.

January 28, 2012
Wang tells Bo that his wife is a key suspect in Heywood's death. Bo responds angrily, slapping Wang in the face. Wang asks his officers to compile evidence related to the case, including blood extracted from Heywood's heart.

February 2
It emerges that Wang is no longer in charge of the police force, although he remains vice-mayor.

February 6
Wang takes refuge at the US consulate in Chengdu for a day in an apparent attempt to defect. On leaving he is whisked away by government officials.

February 8
The Chongqing information office says on its Weibo account that Wang is receiving "vacation-style treatment".

March 5
A Chongqing government spokesman says Wang left the US consulate only after "earnest and patient persuasion" from three top Chongqing officials and a degree of central government intervention. Huang Qifan, Chongqing's mayor, says Wang is being investigated by the Ministry of State Security.

March 8
Bo is absent from the second plenary session of the National People's Congress. The next day he makes his first comments on Wang's case in a question-and-answer session on the sidelines of the NPC meeting, saying he had picked the wrong man for the job. He also talks about Gu, who "basically just stays at home doing housework", leaving him "really touched by her sacrifice".

March 14
Premier Wen Jiabao comments on Wang in his annual news conference at the closing of the NPC session, saying Chongqing authorities should seriously reflect on and learn from the incident, and Beijing took the matter "very seriously". Wang is sacked as vice-mayor the next day and Bo is removed from his post as Chongqing party chief.

March 25
Britain asks China to investigate the death of Heywood. British media report that Wang sought a meeting with British officials hours before he fled to the US consulate. It is alleged Wang told US diplomats about the murder.

April
Bo is stripped of all his Communist Party posts.

July 27
Gu stands trial for murder. In August she is given a suspended death sentence.

September 24
Wang is sentenced to 15 years' jail for defection and other offences.