Five years ago, China's most charismatic politician was toppled from power. His disgrace allowed his great rival to dominate the political stage in a way unseen in China since the days of Chairman Mao.
All this was made possible by a murder.
And the story of that murder begins not in China but in a British seaside town.
It's the summer of 2000 in a resort on the south coast of England, and a well-dressed Chinese woman in her early 40s is trying to buy a balloon. Not a party balloon for the kids - a giant helium balloon like the one right in front of her, carrying holidaymakers 400ft up into the air.
“It was right in the middle of Bournemouth, by the end of the pier in the lower garden, and Gu Kailai just turned up one day and asked to see whoever was in charge,” says Giles Hall, the balloon's owner.
It wasn't a joke. For Hall, this pier-end conversation was the beginning of a two-year effort to satisfy Gu, and he quickly discovered his client was hot-tempered and suspicious.
Gu Kailai on a Bournemouth balloon ride
“We'd have these huge arguments on the phone and she'd say, 'You're threatening me, you're threatening me!' And I'd say, 'I'm not threatening you I'm just telling you the facts!' And one got the distinct impression that if one pushed her too far she could really be dangerous,” he says.
To help with this bizarre business deal, Gu brought in a British middleman who spoke Chinese - Neil Heywood.
One of his tasks, Hall says, was to get the balloon through customs without paying import duties.
“He'd pick us up in a car with a shoebox in the back seat that would have £50,000 ($62,000), which he called his funny money - his bunga bunga money he used to call it for getting things he wanted. It was all very dubious behaviour!
“I used to ask him, 'Where did this come from?' And he just used to tap the side of his nose.”
The balloon was bound for a city called Dalian, which is where Gu and Heywood had first met, several years earlier.
Dalian's stony beach is peopled by hunched figures with steel claw hammers. Through rocks and slime, they dig for worms and sell them, wriggling in plastic cups, to fishermen.
In the 1990s, few people outside China had heard of this gritty port city - next stop North Korea. It was an unlikely destination for a young British expat with an expensive education. Tall and elegant - white linen suits in summer and tweeds in winter - Neil Heywood must have stood out amid the rusting factories and crumbling Soviet-style tower blocks. He started as an English teacher, learned Chinese, found a local wife, and re-invented himself as a business consultant.
I spent weeks interviewing people and no-one could tell me exactly why he was there.
Former British diplomat Kerry Brown, who met Heywood once on a trip to the city, describes it as “puzzling”. There weren't many British business people in provincial China back then, he says, and all of them seemed to have a strange back story.
Neil Heywood's back story may have included a relationship with British intelligence - several sources have told me, off the record, that he worked as an informant. However it's not clear when that relationship began, and British officials refuse to comment. But more on this later.
Here I'm going to come clean. Despite months of trying and hundreds of interview requests all over the world, there are many things we don't know about this story.
There are no heroes in it, only villains and victims. And it's a descent into the dark heart of Chinese elite politics... which is dangerous. Most people who know the story from the inside are dead, in jail or unwilling to talk.
There is a good source, though, when it comes to Gu Kailai's back story - her friend and former colleague, Larry Cheng.
The expensively dressed woman buying a helium balloon in Bournemouth hadn't always been able to count on wealth and comfort, he says. She started life privileged, for sure - her father had been an army general - but then came the chaos and terror of Chairman Mao's Cultural Revolution and, like so many of the Chinese elite, her parents were thrown into jail.
“She was reduced to being a beggar. When her parents were in prison, she was begging outside,” says Cheng. “She did manual labour, she worked as a butcher. She didn't have much schooling but she taught herself and then used her connections to get into Peking University.”
Peking University is the Oxford of China, so Gu was not just a survivor, she was a striver. And after Mao's death her family was back in favour. She'd got the education. She started her own law firm. Also on the checklist - the husband.
At the top level Chinese politics and business are a man's game, so an ambitious woman needs a powerful husband.
When they fell in love he was already married. But the wife was no match for Gu - remembered by Cheng as petite, elegant and very persuasive, a woman who drew a lot of attention wherever she went. The lovers pushed through the divorce, against the wife's protests, and got married.
Back then they lived in a small room without a toilet, Cheng remembers, with a curtain to separate the bed from the table and chairs.
Even the Chinese elite lived humbly in the 1980s. But China was about to hit the big time and so were the newlyweds.
By the 1990s, Gu's husband was China's most up-and-coming politician and serving as mayor in Dalian, the city where Heywood was trying to carve out a career as a business consultant. The mayor's name? Bo Xilai.
Heywood's friend James Richards, once a diplomat in China then a businessman, remembers hearing a story about the young British expat going on a cycle ride and bumping into Bo Xilai - a chance meeting that was the start of a lasting relationship.
“There was goodwill between him and that family,” Richards says. “And China being China I'd be surprised if he wasn't able to ask them to lend a hand here and there with the different businesses he was involved with.”
The discreet lending of a hand is what Chinese politicians and business people do for each other all the time. The politician has the power to grant things like permits and land rights, and the businessman has the money. But they can't be seen to trade. They need intermediaries.
This is the kind of role in which Heywood excelled, notes the Bournemouth balloon man, Giles Hall.
“Neil Heywood had put himself out to any company that wanted to deal in China. He could 'smooth the way', that's how it was put," says Hall.
And he was good at it, Hall says, because he knew the right people.
So let's take stock. There's a young Englishman on the make. There is money to be made. There is a fairy-tale first couple who've now had a son - a dynasty in the making. We're heading for a happy ending, right?
Dalian's seafront can be a lonely place in winter. The Ferris wheel silent, the haunted house empty, go-kart announcements on an endless loop. Gu's life was not the fairy tale that it seemed. Because behind all the communist pieties about humble living and public service, Chinese politics was back to what it had always been over the centuries - a game of power and sex.
Gu Kailai told Larry Cheng that Bo was unfaithful.
“Every day she felt sad and lonely. She even tried to kill herself because the man she loved was having affairs,” he says.
“She had a scar on her wrist from a knife. She was trying to scare Bo. She was in such low spirits, so she took sleeping pills and tranquillisers. She drank a lot, too."
And like discarded empresses and concubines throughout imperial history, Gu started to look elsewhere for love. Chinese literature even has an expression for women in her situation - the red apricot.
“She was a red apricot leaning over the palace wall and down toward the street. In the beginning, I think Kailai was the typical wailing woman in the palace, then she leaned out to the street. She lost all principle. If any man was useful to her, she might take him as a lover. Her personal life was a mess,” says Cheng.
In Dalian many people told me - off the record - about the long list of lovers.
In 1999 Gu turned her back on her loveless marriage. From then on, she and her husband would be a partnership in public only. Restless in the confines of provincial party politics, she made it her goal to turn her son into a member of the global elite. And where better to learn the English of the ruling class than in England? Through her contacts she found a language school in Bournemouth and rented a top-floor apartment in the resort. It was in a grey concrete block opposite an Italian restaurant called Valentino's.
Owner Giuseppe Flacchi says she visited the restaurant often, but never smiled and always seemed very busy.
Gu did her business round the red checked tablecloth. Moving money out of China through tax havens and into property in the West, with the help of a shifting cast of intermediaries, including Heywood.
Valentino's restaurant, Bournemouth
It's what many elite families were doing - getting their kids and money out of China. So Gu wasn't the exception. She was the rule. And it all made a big impression on Giles Hall.
“We used to have meals in the Italian restaurant with Gu Kailai and Neil Heywood and she would often lose her temper. She'd say things like 'Have you transferred that money to New York to X? She needs that $14m!'” says Hall.
“And I remember thinking '$14m!' and I looked at my secretary and she couldn't believe it either! And he'd say: 'No, I'll do it next week.' And she flew off the handle and shot out of the restaurant.”
Where was the $14m coming from? Gu didn't have a job any more and her husband, the mayor, was - officially - earning about $18,000 (£15,000) a year. But for those in power, there's no shortage of money in China.
One thing Gu needed money for was her new project - getting her son an expensive education at one of the grandest British private schools, Harrow.
She asked Giles Hall if he would add £240,000 ($290,000) to his company's invoice for a helium balloon and then give her the money to pay the school fees, but he refused.
“She threatened all of us and said, 'My friend is the police chief in Dalian and if you ever come to China again I'll throw you in jail and you'll never see the light of day.' I had protection for some while because she got very, very threatening."
Giles Hall isn't the only person in Bournemouth who has lurid stories about Gu's money laundering - boxes full of cash, private jets, threats - though most are scared to speak on the record.
There were occasionally tensions between Gu and Heywood, Hall noted.
He got a sense that Gu didn't fully trust her British business fixer to transfer funds, and not to keep something back for himself.
“I think he had got greedy," Hall says.
And don't forget the story of the red apricot. In Bournemouth Gu went on having affairs with those who proved useful. We don't know whether that included Heywood. But their relationship was certainly intense.
“He always said to us, 'If she ever does anything to me, I'll have her throat cut,'" says Hall.
"He was a great threat because he knew everything that went on. Knew all the shenanigans, the way money was shifted around, bank accounts - knew everything."
Bo Xilai always stood out.
Tall and handsome, as a young man he never seemed to stop smiling.
“Bo Xilai was the biggest figure in my class,” says Gu Jian, who shared a desk with him for three years at journalism college in Beijing. He remembers the day they met - the first day of term in 1979 - and so does one of their old teachers, an American, Stephen Mackinnon.
“He was tall, gawky, very simply dressed, kind of bony - he had a big head,” Mackinnon recalls. “And he was always kind of smiling. Eager to take on the world.”
Bo with his friend Gu Jian, 1979
Like Gu Kailai, Bo was a member of the communist aristocracy, his father Bo Yibo a hero of the civil war that brought the communists to power.
But during the Cultural Revolution Chairman Mao threw Bo Yibo in jail. Bo Xilai's mother committed suicide and he himself lost a decade shovelling coal. Then Mao died, China woke up, and Bo could start planning a political career. Aged 30 he finally got to university.
“They dressed like workers... very ordinary, in beat-up clothes. We were living in dorms. It was pretty simple - not fancy, that's for sure,” says Mackinnon.
Mackinnon remembers how Bo became a hero for his classmates when he turned up to a picnic with two cases of beer, then in short supply but still available in Zhongnanhai, the closed compound where top leaders live and work.
Bo lived like other students during the week. But his dad was now out of jail and back at the top table, so come the weekend he returned to that high-walled, secretive compound for the elite.
Sometimes he took his classmate, Gu Jian, who marvelled at their satellite dish. He'd never seen one before, or been in a house showing foreign broadcasts on six TV screens.
Only a few years earlier, under Chairman Mao, even listening to foreign radio could have got you executed.
But the perks didn't stop at satellite TV. Sex was also part of this life of entitlement. At this point Bo was already married - to his first wife. But being married never stopped him from playing the field - and a reputation for sleeping around didn't go down well with the communist old guard, to say nothing of his wife and her powerful family.
One day Bo called Gu Jian complaining of a fever and asked him to visit him in Zhongnanhai. As Gu Jian walked into Bo's house, the guard outside told him to persuade his friend to stop having affairs.
Bo was on to his second wife - Gu Kailai - by the time he got his first big job, as mayor of Dalian, in 1994.
He was a mayor like no other. He turned a rust-belt port into a green and modern city. He built museums, five-star hotels, parks and squares. He was more like an emperor than a mayor, and his old teacher Stephen Mackinnon came to the emperor's court to see what all the fuss was about.
“He said you've got to do three great things to make your city noticed,” Mackinnon remembers. “You want to have green everywhere. You want to have China's best football team. And the other thing is fashion shows.”
Bo used government money to set up a modelling school filled with gorgeous young women, and then put on fashion shows to prove to his visitors just how beautiful Dalian was. Not just the greenery and the museums but the women too.
“He surrounded himself with beautiful women. If you weren't beautiful you couldn't work for him,” says his wife's friend and former colleague, Larry Cheng.
“He stayed late at work and hardly ever went home. His office lights were always on even in the middle of the night. The people of Dalian thought he was working so hard and said they had a great mayor. But he was probably up to something with those beautiful women.”
I've talked to several government people in Dalian who say Gu did a good job of scaring off at least one rival. They also say there were young models who simply disappeared. I couldn't get to the bottom of these rumours.
But this is China. If you control a city, you control the police, the courts and the media. You can make people appear... and you can make them disappear.
One man who has first-hand experience of this is Dalian businessman Zhang Yongxiang. One moment Bo wanted Zhang's help in taking down one of his enemies, the next he had become an enemy himself, finding out what it meant to incur the mayor's displeasure.
He says Bo set up a team of interrogators, who tortured his family, forcing them to endure nine days and nights of interrogation without sleep.
Sixteen members of the family were detained, and police were hunting for more.
“My cousin was on the train from Dalian to Shanghai to take my sister-in-law to hospital. On the way back, he somehow fell off the train and was killed,” says Zhang. “The police said he jumped. But I don't believe them. Did they beat him to death? Did they shoot him dead? The police owe us answers.”
And until they get those answers, the family refuses to bury the body. They've been waiting 15 years.
That's the dark side of Bo Xilai's Dalian. None of it was visible to the public. As far as they were concerned they had a perfect mayor and he had a perfect wife. Charming, good-looking… one Western businessman who worked in Dalian in those days compares them to JFK and Jackie Kennedy.
Though their marriage was by now a sham, husband and wife still kept up appearances for the sake of the power and the money. But Dalian was never going to provide enough of either.
Bo had his sights on the Chinese leadership and by 2004, he was playing for China on the international stage. He'd been promoted to minister of commerce - a job that put him across the negotiating table from European trade commissioner Peter Mandelson.
“Power exuded from him. It surrounded him. When you were dealing with him you felt you were dealing with the main man,” Mandelson remembers.
The two men were trying to hammer out a crucial deal on textiles, and this story tells you everything you need to know about Bo the operator.
“At first Bo was completely unhelpful. No, no, no and no were the answers I got,” says Mandelson.
Then suddenly, when he was at a meeting in Cairo, he got a call to say Bo would see him in Shanghai in 48 hours.
Mandelson hurried to Shanghai - changing planes, struggling to prepare for the meeting, but relieved that Bo was at last prepared to talk.
“He'd lined up 100 officials down one side of a table in the state guest house in Shanghai,” says Mandelson. “I arrived with three men and a dog as my team.”
The negotiations went on for 12 hours, during which Mandelson and his colleagues were given very little to eat or drink. The Chinese team were all being handed large vitamin C tablets, but these were not offered to the Europeans.
Finally an agreement was reached, and a huge press conference was held to announce the result at four o'clock in the morning.
“I think Bo knew exactly what he was going to end up doing,” says Mandelson. “He knew what sort of agreement he would eventually embrace. I was kept completely in the dark until the last moment when finally he did the business.”
The timing was great. A big national leadership change was coming up and Bo hoped to make it to the very top - the standing committee of the Communist Party politburo, where a handful of men make all the key decisions.
Backing him was his father, a revered and still immensely powerful party elder. Seriously elder - 98. And then, just when Bo needed him most, the old man died.
Chinese politics is all about the patriarch, the clan, the tribe. The loss of his father left Bo exposed.
Gu Kailai and Bo Xilai at his father's funeral
There were so many people he had crossed. His jilted first wife and her powerful family, the communist old guard who were scandalised by his sex life, and many more. He drove his juniors hard, he undermined his seniors. And then there were his political rivals - the men who were also fighting for a place at that top table. These enemies now united against him.
He was posted to Chongqing, a city 1,000 miles from Beijing and notorious for its gangsters, gambling and vendettas.
But Bo's biggest problem in Chongqing would not be the crime gangs and their political backers but the woman at his side - his wife, Gu Kailai.
In November 2011, four years after the move to Chongqing, and more than a decade after their balloon-buying days in Bournemouth, Gu summoned Neil Heywood from his home in Beijing to Chongqing.
Before Heywood left, he had dinner with his old friend, James Richards, who noticed that he was becoming increasingly disenchanted “with the natural entitlement to privilege and power that he found among these people”.
“He certainly found the atmosphere of distrust, suspicion, back-stabbing increasingly oppressive. My last meeting with him, I remember coming away thinking he did seem quite unhappy and depressed and anxious,” Richards says.
Heywood didn't leave China. On 13 November 2011 he boarded a flight to Chongqing. Sitting next to him was Gu Kailai's loyal servant - a man who knew what was about to happen in the Lucky Holiday Hotel.
Bo Xilai didn't want to be out in the sticks. If he couldn't hog the spotlight in Beijing, then he was going to bring that spotlight with him.
His old teacher, Stephen Mackinnon, was struck by his one-time student's refusal to keep his head down and accept political defeat.
“When he went to Chongqinq he's going to make a splash and go for it and really grandstand or do dramatic things,” Mackinnon says.
“He must have known it was risky. He felt he'd been marginalised and they were putting him out to pasture, so what the hell!”
The whole of China looked on spellbound as Bo did something no-one had dared to do since Mao. He went above the Communist Party machine and spoke directly to the public.
He dusted off the propaganda campaigns of early communist China. He had Chongqing singing Mao's songs at mass rallies - 100,000 people amid a sea of red flags. Disgusted by the corruption that had flourished under previous leaders, the public loved it.
But it wasn't just political theatre that Bo brought to Chongqing. He also started improving people's lives - building roads, fixing street lamps, cleaning the city. He raised salaries and improved healthcare.
For this he needed money and one way he got it was to "arrest rich people, call them criminals, and confiscate their assets", says Li Zhuang, a high-flying lawyer who represented some of the targets.
"Apartments, villas, office buildings, cars, bank deposits - everything would be confiscated. For a small crime boss tens of millions. For a big crime boss it could be more than 100 million... overnight.”
Bo arrested thousands and executed powerful people. Again, the public loved it.
But in China, no politician can go after the rich and well-connected without the support of the chief of police. For this role, Bo had found the perfect partner, a man both ruthless and daring - Wang Lijun.
Wang arrived at crime scenes brandishing weapons and surrounded by TV cameras. He even had his own show - Iron-Blooded Police Spirit - which dramatised his life fighting crime.
And it gets weirder. Wang Lijun attended executions, sources tell me, supervised the harvesting of prisoners' organs and even conducted his own post-mortem examinations.
“Wang and Bo were very similar. Both of them liked to do things on an epic scale, they liked to make headlines. Put them together and it was an explosive mix,” says Li Zhuang.
In China, the police like their headquarters to look intimidating. But even by Chinese standards, Chongqing's is massive.
Wang didn't just work in it, he lived in it. He was paranoid. He thought people were out to get him and so, his staff say, his secretary had to taste every plate of food he ate, even down to sipping his cups of tea to make sure they weren't poisoned.
A paranoid narcissist living in a fortress and blurring the line between fact and fiction.The people of Chongqing will not forget Wang Lijun quickly.
Chongqing's riot police in training
Lawyer Li Zhuang has even better reasons to remember him than most, because the police chief turned up in person to arrest him on the tarmac at Chongqing airport - surrounded, of course, by TV cameras and with a film-ready script.
“The scene was so over-the-top, loads of police cars surrounding the plane, riot police in helmets and camouflage, armed with submachine guns. I asked, 'Why the big show? Is it Obama's state visit or are you capturing Osama Bin Laden?'
“We were surrounded by a huge scrum of reporters. He wanted to show his authority on camera. He was in a trench coat, hands in his pockets. He said: 'Li Zhuang, we meet again.'”
Li Zhuang was jailed for 548 days - a year and a half. He says he thought he would die in Chongqing, and that Bo and Wang would rule China.
Gu and Wang
Ruling China was certainly Bo's ambition. He had been on the 25-man politburo since 2007, but to go even higher he needed to do more than lock up gangsters and their lawyers. He had to take the fight to his political enemies in Beijing. With a loyal police chief by his side, Bo thought he was a match for them.
But in room 1605 of the Lucky Holiday Hotel, someone miscalculated.
On 13 November 2011 Neil Heywood was murdered.
Three days later a fax from the local police arrived at the British consulate in Chongqing. It said a 41-year-old UK citizen had died of excessive alcohol consumption.
Gu Kailai had moved to Chongqing to play the part of the politician's wife. But in the frenzied climate of that city she had become ever more isolated and paranoid.
Heywood told his friend James Richards that Gu thought she and her husband had been poisoned and were going to die, making her “depressed and angry and vindictive”.
And at some point, the fragile trust between Gu and Heywood had broken down completely.
“From what Neil said, the estrangement was very clear and definite. And I think it was painful to Neil,” says Richards.
The prospect of somehow resolving the issues between them was probably what led Heywood to travel to Chongqing, he says.
Villa number 16 of the Lucky Holiday Hotel is at the end of a cul-de-sac, surrounded by vegetation - a secluded and lonely corner of this government-run hotel complex on an isolated hillside.
On the day I visit, security guards are very agitated. They don't want me here. Before long three are surrounding me, and others are watching from a balcony. Amid the shouting, I cannot get a word in edgeways.
“PLEASE Go! Go! Go! Go, go go go. Out! OK?” shrieks one.
The manager tells me to put my questions about Neil Heywood's death - to Neil Heywood.
“How can I talk to Neil Heywood when he's dead?” I ask.
He laughs and tells me to go to hell to look for Neil Heywood there.
Five weeks after the death, a memorial service was held at a church on the banks of the River Thames in London.
There was no body to bury. It had been cremated - without a post-mortem - two days after the British consulate had been notified of the death.
And the cause of death was unclear. While the fax from the police to the British consulate had given the cause of death as “excessive alcohol consumption” Heywood's family had been told that he died of a heart attack.
James Richards did not believe either story.
Heywood was 41, slim, and did not look like someone who would have a heart attack, he says. Nor was he a great drinker.
“When I heard that he'd died in Chongqing, and further that his body had been cremated soon after his death, my suspicions grew,” Richards says. “To the point where if I'd been asked to place a bet one way or the other, I'd have said I believed he was likely to have been murdered.”
Back in Chongqing, it was business as usual. Police chief Wang Lijun had done his job - forensic evidence had conveniently disappeared, the body had been cremated and officers silenced. No problem.
But then something went very wrong between the politician, his wife and his police chief.
Twelve weeks after the murder, Wang was running for his life. On 6 February, the man who normally loved the limelight got into his car under cover of darkness. Disguised as an old woman, he drove 320km (200 miles) to the nearest US consulate, in Chengdu, and begged for protection. He told an astonishing story.
Wang Lijun told the Americans that Gu Kailai had murdered Neil Heywood - and that Bo Xilai was now out to murder him.
US diplomats found themselves thrust into the middle of a Chinese political drama, their consulate practically under siege.
Growing numbers of armed police cordoned off the streets around the building, some loyal to Bo, others to his political enemies in Beijing. Both wanted control of Wang and his explosive story.
The decision about what to do with the would-be defector was a delicate one for US Secretary of State, Hillary Clinton.
Wang did not meet the conditions for asylum, she said later, noting that he had a record of “corruption, of thuggishness, brutality” in his role as an “enforcer” for Bo.
The Americans chose to give Wang to Beijing, and he disappeared into detention.
Everything now began to unravel for Bo and Gu. Bo was removed from his post as party boss of Chongqing, while on 10 April came a sensational double blow. Bo was suspended from the politburo, and simultaneously Gu was arrested on suspicion of involvement in the murder of Neil Heywood.
It was China's biggest political crisis since the Tiananmen Square crackdown in 1989, laying bare a savage struggle at the top of the Communist Party.
Three spectacular show trials followed.
First in the dock, in August 2012, was Gu. She was charged with murder, and made a full confession. From her testimony, and that of her assistant, this is the picture that emerges from the evening of Heywood's death.
A car takes him from the airport, along Chongqing's new highways and up a winding mountain road to the Lucky Holiday Hotel villa complex.
Heywood and Gu have dinner, and in his room they share a nightcap. Heywood gets drunk, staggers to the bathroom, and slips over in his own vomit.
Gu calls in her assistant who's been waiting outside the bedroom door - the same person who accompanied Heywood from Beijing. Together, they drag Neil Heywood on to the bed.
He begs for water. Gu drips poison into his mouth. She waits until she can no longer feel Neil Heywood's pulse. And then she scatters pills around the room to make it look like an overdose.
And as she leaves she hangs the “Do Not Disturb” sign on the door.
The trial lasted a mere seven hours and foreign reporters weren't allowed in. All we've got to go on is an account released by the court - and it's worth pointing out that in China the Communist Party controls the courts. Everything that happens is decided in advance to suit those in power.
“This case has been like a huge stone weighing on me for more than half a year. What a nightmare,” Gu said in her testimony.
She committed murder, she told the court, to protect her only child, Guagua, because his life was under threat from… Neil Heywood.
Guagua's life had been mapped for greatness. He was born into a political dynasty - the Bo family - at a time when China was fast becoming a world power. He started life among the Chinese elite, but his mother had bigger plans, which is why she took him, at the age of 12, to the UK.
Guagua made an unfavourable impression on Giles Hall, the Bournemouth balloon operator, who met him often during business meetings with Gu.
Gu, Bo and their son Guagua
“The child was very hard to like, I have to tell you. He was described by Neil Heywood as an 'arrogant prick'. Which he was,” Hall says.
“He wouldn't look you in the eye, he wouldn't shake your hand. He'd be rude to his mother in her company with you. Everybody who was around him was treated as subservient.”
Guagua was always asking for more pocket money, Hall says, so Gu would give him £500 - which Heywood would pay out in £50 notes - just to keep him quiet.
It was Heywood who helped arrange for Guagua to go to Harrow, his old school. After Harrow, Guagua went to Oxford University, where he gained a reputation as a party animal, and was kicked out of his college for a year for falling behind in his studies. But he just spent the time in a five-star hotel a few hundred yards down the road and was eventually allowed to return to sit his final exams.
Then he was off to study law at Harvard.
Throughout this period, with Guagua's parents thousands of miles away, Heywood remained someone he could turn to. Whether or not he continued to regard him as an “arrogant prick”, on the surface their relationship was cordial.
So what evidence was there for Gu's claim that Heywood was threatening Guagua?
It all came back to the money. In the transcripts of the trials, Gu admits that Heywood helped her hide assets abroad - money that was moved secretly into property in the West, and paid for Guagua's lifestyle and education.
But when she finally sought to to sever their financial relationship, he demanded a payment of $2m (£1.4m). The court was shown an email in which he threatened to “destroy” Guagua if he didn't get it.
So she killed him.
Initially she and the police chief had discussed framing him as a drugs smuggler and killing him in a staged shoot-out at the airport. Only later did she turn to poison.
“I had to fight to the death to stop the madness of Heywood,” as she put it.
But it was her own madness that she had to prove in order to avoid the death penalty. The official account detailed her insomnia, depression and paranoia. It cast her as a deranged, drug-dependent mother driven to murder a man she believed threatened her son.
It worked. She was found guilty of poisoning Heywood but she got off with a suspended death sentence, later reduced to life in prison.
Former British diplomat and Chinese politics expert Kerry Brown was left with many questions. He asks what people would think in the reverse case - if a Chinese citizen had been murdered in a hotel, by the wife of a British cabinet member.
“I mean would anyone accept the story that was eventually told? The one day of testimony... I felt it was hard to say that was an exhaustive process,” he says.
British Foreign Secretary William Hague had described the death as one that “needs to be investigated on its own terms, without political considerations”. But Brown says the British government failed to ask tough questions, and to get a complete record from the Chinese of what happened. Or if they did, it wasn't made public.
Conspiracy theories abound.
Some think Bo ordered the murder. Others blame the police chief. There are even some who say the woman in court was not Gu but a body double.
And there are those who argue that Heywood was murdered because he was an informant for British intelligence. Of course, this factor was never mentioned in court. It wasn't in the Communist Party's interest to reveal that one of its top families had been penetrated by foreign spies.
It's a matter of public record that Heywood occasionally worked for a consultancy firm called Hakluyt, founded by former British spies.
I also spoke to a number of people who said, off the record, that Heywood regularly passed information to British intelligence officers.
Sir Richard Ottaway, who was chair of Parliament's foreign affairs committee when the spy reports surfaced, was told by the Foreign Office that officials had carried on an “informal relationship” with Neil Heywood, and “had taken information”.
“I think it would have been pretty dilatory for MI6 not to have had contact with him and perhaps a drink after work to pick his brains about what was going on,” Ottaway says.
I wanted to ask the UK government directly about this relationship. And about why, when the British consulate in Chongqing learned of the death in the Lucky Holiday Hotel, there was no demand for a post-mortem of a British government informant - not to mention a 41-year-old moderate drinker who died from over-drinking, as the Chongqing authorities had originally claimed. But the UK government declined to talk to me.
Bo Xilai went on trial in August 2013. It was an electrifying moment in the normally sanitised politics of China.
He was not accused of Neil Heywood's murder, or even with covering it up. The charge sheet - bribery, embezzlement and abuse of power - was the standard one used against a Communist Party boss. It was a classic Chinese political takedown.
Every detail was carefully planned. The 6ft-tall Bo stood in the dock flanked by even taller guards, clearly chosen in an effort to make him look small.
But Bo appeared as confident as ever.
His former police chief, the gun-toting narcissist Wang Lijun, who had fled to the Americans disguised as an old woman, was the star witness, called to the stand to betray his old boss.
He described a dramatic confrontation that took place 11 weeks after the murder.
“Bo punched me. My mouth was bleeding, there was liquid dripping out of my ear.
“I told him calmly that he needed to face facts. He picked up a glass and smashed it on the floor, and said he could not accept it.”
Again, foreign journalists were not allowed in, so these words come from a partial transcript released by the court.
Bo wasn't angry about the murder or the cover-up. He was angry because his once loyal police chief had kept forensic evidence pinning the murder on his wife, and a tape of a conversation with Gu secretly recorded the day after the crime.
But assaulting Wang was Bo's fatal mistake, the trigger that prompted him to run to the Americans in fear of his life.
Without this mistake the world would know nothing of Neil Heywood's murder, the Communist Party not choosing to wash its dirtiest linen in public.
The attempt to defect was a huge risk for Wang to take - one that could easily have got him killed. So why did he do it?
It's time to turn to Bo's enemies.
Neil Heywood's murder took place at a critical moment. Xi Jinping was due to become Communist Party leader and Bo was again fighting for a place at the top table, the politburo standing committee.
If he had made it, he might have outshone Xi - a man he had grown up with at the very top of the party. His longstanding rival.
“At the elite level they all live together, eat together, they do everything together. There are linkages we wouldn't normally expect. It's like a massive sort of gentleman's club. Like a really, really big family,” says Chinese politics expert Kerry Brown.
Bo was better-looking, a more charismatic politician from a more powerful family. From the outside, the obvious winner.
But success in Chinese politics has always been about finding your rival's weak points. Here Xi outplayed Bo. The murder in the Lucky Holiday Hotel became Bo's weak point.
“Xi Jinping, his supporters and those who hated Bo Xilai crafted this case together,” says journalist Ho Pin, who wrote a book about the murder.
It was “fantastic good fortune” for Xi Jinping to have this tremendously popular politician removed, says Brown.
“Bo Xilai, if he'd still been around, would have been a powerful personality to look at - how amazing that he just got removed in this very big way. This may mean Xi is a lucky politician - that's possible - or it may mean that the whole thing was manipulated.”
None of this came out in court. The prosecution carefully avoided asking this key question: why had Wang Lijun suddenly confronted his boss with evidence of Gu's guilt, more than two months after Neil Heywood's murder?
The most likely explanation is that Bo's enemies were leaning on Wang. They'd already arrested some of his former officers. Wang was afraid he was next and asked his boss for protection - but Bo refused.
“Wang Lijun was Bo's dog, following wherever he goes. He was born to be a subordinate,” says lawyer Li Zhuang.
Bo didn't have time for the problems of his dog. He was in the fight of his life for a place at that top table. But the pressure kept coming on Wang. Give up Bo or else. The best dirt he had on his boss was the murder - a murder he had himself covered up. Any evidence against his boss would also incriminate him.
So Wang went back to Bo for protection. But instead of offering protection, Bo punched him for his impertinence. Bo now knew that Wang had evidence that would destroy him and knew his enemies were closing in.
“Bo would have Wang Lijun killed and cover up the murder,” says Li Zhuang. “Then he'd hold a memorial and publicly mourn him, saying his police chief made the ultimate sacrifice on the front line of the gang crackdown. Bo is a fantastic player.”
But Wang escaped.
It would take 18 months to construct the case that would finally destroy Bo.
Because he provided the crucial evidence Wang got off with a mere 15 years. Bo was sentenced to life in prison.
According to James Richards, the Heywood scandal “altered the course of Chinese history”. It gave Xi Jinping the perfect opportunity to remove a rival from the party hierarchy and to purge those around Bo Xilai who might also have challenged his growing power.
Officially Xi is now “the core of the party leadership”. Unofficially the “chairman of everything”.
This concentration of power and prestige would have been much harder to achieve with Bo competing for the limelight.
Xi has used his good luck to enforce “a repressive regime”, Richards notes, while showing “an almost obsessive desire to control everything – society, media, information - which could threaten the party".
My colleagues and I were under surveillance for months as we investigated this story. People whose experience I respect warned me it was dangerous.
When I went to Chongqing to look for insiders who could tell me about the fall of Bo, only one person - in a city of 30 million - was prepared to talk.
We were followed, our phone calls were bugged, and the Communist Party propaganda officials got to everyone, even to my one and only interviewee, before I did.
I knocked at his iron-clad door and was met by silence. When the party's enforcers have done their job of intimidation, this what you get. People are rightly scared.
Xi's information control may extend even to the UK, if James Richards's experience is anything to go by. As godfather to one of Neil Heywood's children, Richards tried in vain to get compensation for the family, and had a folder on his computer containing hundreds of emails. It was labelled "Chongqing incident”.
He'd always taken it for granted that telephone conversations or emails sent to China from the UK might be intercepted, but he hadn't foreseen that his hard disk was at risk. And yet, one day, when he switched his computer on, the Chongqing folder had gone.
Welcome to Xi Jinping's China
Bringing down Bo Xilai and others allowed Xi Jinping to present himself as a decent man cleaning up corruption in a decadent party. But Xi has a past too.
And as we've seen, the real story is more complicated.
You could go so far as to ask, did Gu Kailai even do it - or was she framed? Don't expect the story to change as long as Xi is in power. But afterwards? Anything is possible.
China is a country where verdicts can be reversed, and where “one truth is replaced by another”, as James Richards puts it.
A case in point: Bo Xilai sits today in the same prison that once held his father, and when the political wind changed 40 years ago his father was released and reinstated at the top.
The Bos are a dynasty. And the next generation is not behind bars. Good-time Guagua will be 30 this year. He has recently graduated from Columbia Law School and is lying low in Canada, but law school friend Timothy Kim says Guagua has not forgotten who he is.
“He plays it kind of coy. But it seems like he wants to go back at some point to China, and be engaged on some level in either policy or politics,” Kim says.
“After everything happened with his family he made a shift in his life and became a lot more reserved. He's a little bit more serious about what he wants with his career.”
Kim draws attention to Guagua's Facebook page.
“It's very sparse but his profile picture is an old photo of him and his father. I thought that was telling about his general thoughts about his family and his feelings towards what happened - and perhaps where he'd like to be in the future.”
Find out more
Listen to Carrie Gracie's podcast series Intrigue: Murder in the Lucky Holiday Hotel on BBC iPlayer Radio
Maria Byrne & Wei Zhou
Getty Images, Reuters, Associated Press, Alamy, Shutterstock, iStock, EPA, Larry Cheng, Peter Dean/Flickr, New York Times