If ever a moment summed up the parallel universe Chinese president Hu Jintao inhabits, it was when he spoke at Yale university in April 2006, at the end of a US tour. Hu told his audience that the visit to New Haven had triggered a sense of nostalgia in him for his "great experiences" at Tsinghua university in Beijing 40 years earlier. There are parallels - Tsinghua has an elite pedigree and holds a similar status in China to Yale in the US. But Hu's final years there could not have been more distant from the images of idealistic inquiry he alluded to at Yale.

His last three years at Tsinghua, working as a "political counsellor" after completing his engineering degree, overlapped with the early days of Mao Zedong's brutal cultural revolution. This was no summer of love. Using gangs of Red Guards, Mao Zedong's cataclysmic campaign wiped out political opponents and destroyed the lives of millions of Chinese in an effort to cleanse the party of so called "intellectual" and "bourgeois" influences. And yet, as Tsinghua was overrun by radical activism and denunciations of academics, Hu survived. Of the four political counsellors in his year at Tsinghua, "only Hu Jintao was called 'commander'," recalls Wan Runnan, a university colleague at the time.

"He had no enemies at Tsinghua," says Wan. "No one would consider him a rival. He was skilful in giving you face [a Chinese idiom for showing respect]. He would make comforting remarks when you made errors. This is why he had a good reputation among students.

"Those same skills were on display again five years ago, as Hu rose to the top of the Chinese leadership: deference to elders, a strategic accommodation of enemies, mastery of the prevailing party rhetoric and a beguiling blandness. Now, at the end of his first term as president of the world's most populous country, it is that last quality that dominates: on the eve of his appointment for a second five-year term, at the Communist party congress starting October 15, Hu remains a determinedly enigmatic figure devoid of flesh and blood. While his country has charged helter-skelter into the 21st century, Hu has managed his personal political image like a pre-modern emperor.

But whereas a second-term president in the US is often a lame duck, in China this is a period when leaders begin to accumulate real power. Hu, the enigma, politically, if not personally, could still emerge from the shadows.

Other Chinese leaders have been different. Deng Xiaoping had a revolutionary prestige, overlaid by the battle scars of years of struggle against Mao's insane political campaigns. He proudly displayed his earthy Sichuanese roots, notoriously expectorating loudly into his spittoon while delivering a lecture to Margaret Thatcher about Hong Kong at a meeting in Beijing. Jiang Zemin, meanwhile - Hu's immediate predecessor - delighted in singing in public and reciting from the Gettysburg Address in English. A British official remembers Jiang as mayor of Shanghai, bouncing into his office and declaring his disappointment at finding, on a visit to the UK, that he could not see London Bridge - a mythical monument in the eyes of the Chinese - because it had been packed off to Arizona by the unsentimental British.

Hu displays neither a down-to-earth vigour nor a clownish chumminess. He has no accent to signal his regional roots. In meetings, he is courteous, meticulous and focused, thoroughly in command of the facts. But he gives little away. "Hu Jintao will not give a very clear view, or talk about the situation very clearly," says Liu Rixin, a retired planning ministry official. A British government adviser says: "The impression he gives is one of extreme competence."

On rare occasions, Hu has displayed a sharp, self-deprecating sense of humour. On Hu's first trip to the US in 2001, James McGreevey, the youthful then New Jersey governor, admiringly contrasted his own greying locks with Hu's jet-black hair. Hu, according to someone at the meeting, quipped: "I am sure China would be happy to share its technology in this area." (Like all Chinese leaders with even a hint of greying locks, Hu dyes his hair black.)

But the most important quality about Hu may the one that snuck out in the rosy recollections of his Yale speech: his singular belief in the Communist party, a view unshaken by the cultural revolution and the frenetic modernisation of much of the economy since then. In the lead-up to the October congress, a number of retired party figures have been agitating for a more open political system, in keeping with China's increasingly complex society and economy. But Hu's fixation on the party as the sole institution with the standing, the ability and indeed the right to guide and govern China, remains as unshakeable today as when he joined nearly half a century ago.

"Hu Jintao moves in self-reinforcing circles," said a European ambassador. "When he comes to the office in the morning, he has only one newspaper on his desk that he reads, and that is the People's Daily" - the party's official mouthpiece.

Arthur Waldron, a China historian, sees Hu as the ultimate product of an increasingly professionalised and calcified ruling party. "We have much of a muchness, literally hundreds of men of a certain age, having an OK, but not outstanding, education, little by way of travel or foreign languages, lots of experience administering measures imposed by someone else's power and good at conformity," says Waldron.

A closer study of Hu's life and times reveals some method in his measuredness, as though he has long sensed he was predestined to rise to the top. "He has been watching what he says since he was a teenager," said Ma Ling, a Beijing-based biographer. At home he appears only in tightly scripted appearances with specific political messages. He has given no interviews as president, apart from answering a few prepared questions from Russian reporters, and the few press conferences he has held overseas have been limited to one or two pre-screened questions.

A foreign diplomat recalls planning a G8 meeting that Hu would attend and which was supposed to be informal and free flowing. His Chinese interlocutor balked: "President Hu does not do free-flowing." When I visited the new Communist party school this year at Yan'an, a famed revolutionary base, the officials in charge showed us a video of Hu giving his impromptu ideas about what the institute should be teaching. For my Chinese assistant, a young man who, like many of his contemporaries, is thoroughly wired into everything the media in the internet age has to offer, the video was a shock, as he had never seen his president speak off the cuff in a relatively informal setting.

Every effort has been made to shut doors on Hu's life. Ma's book was more hagiography than biography, but she was rebuked for writing it. Hu's university contemporary Wan, who founded one of China's first computer companies, Stone, speaks freely only from exile in the US, where he has lived since the crackdown on pro-democracy demonstrators in 1989. And while the few foreign reporters who have managed to speak to Hu's aunt, Liu Bingxia - who raised him from the age of five in the city of Taizhou, Jiangsu province, after his father died - returned with a consistent image of a diligent and uncomplaining boy, even these insights were too much for the authorities. Local officials have since prevented visitors from talking to her. That may be because of her age (she is now in her nineties), but is more likely to stop information getting out. Officials even took the precaution of visiting her house when Hu's political star began to rise, to confiscate family pictures of him as a young man.

Reading between the lines, Hu's survival of the cultural revolution virtually unscathed suggests that a running caricature of his late father, a tea merchant, as a successful businessman is false. "His father was a merchant who failed," says Ma. "If his father was a big capitalist, he would have been shot."

Liu Yongqing, Hu's wife, is as self-contained as he is, and they have scrupulously kept their two children out of the spotlight - even after their daughter, Hu Haiqing, married a multi-millionaire internet entrepreneur, Daniel Mao. Their son is believed to work for a local IT company. This tight media management has built an imperial-era image of Hu, like a benevolent emperor whose interventions are as wise and weighty as they are rare. It also makes his politics hard to unpick. To many, this is a deliberate strategy that enables him to avoid taking any blame for decisions by appearing to transcend the day-to-day work of the government.

Some clues about his beliefs can be found by following his path after he left Tsinghua university, dispatched to the countryside to work (the fate of many educated people in the cultural revolution). Hu spent the next 14 years in Gansu, a barren province on the edge of the Gobi desert, building dams and working in the party's propaganda department. "He saw how poor people lived, and how miserable their life was," says Ma.

It was in Gansu that Hu was spotted by Song Ping, a party elder who later recommended him to Deng. When he returned to Beijing, he was soon appointed to head the Communist Youth League, which remains his power base to this day. There, he gained another patron, Hu Yaobang (no relation), a popular reformer as party secretary whose death later sparked the Tiananmen Square protests of 1989.

With patrons such as Deng and Hu Yaobang, Hu was firmly identified with the liberal camp, and on the way up. At 39, he became the youngest-ever appointee to the central committee. When he was dispatched to run Guizhou, another impoverished region, in the mid-1980s, he went as the youngest-ever provincial party secretary.

Ross Garnaut, then the Australian ambassador, remembers long conversations with Hu in Guizhou about agriculture. "He was very interested in lessons and insights from international experience, and deeply committed to the reformist approach in rural development," says Garnaut, who also arranged for Hu to visit Australia in the 1980s, in what is believed to be his first trip to the west. "He enjoyed being a guest at Government House in Melbourne, as a humble party secretary from an out-of-the-way province."

At the youth league and in Guizhou, Hu ran into entrenched interests suspicious of the smooth young newcomer. But his soothing political style appears to have disarmed opponents. "I remember visiting Hu in 1985 in Guizhou, when he proudly told me how he managed to make every faction happy, and treat every party member according to an equal standard," says Wan.

Hu's economic report card in Guizhou is less flattering. A 2002 article in the Southern Weekend, a Guangdong newspaper, detailed the destruction of some of Guizhou's best farmland by the proliferation of coke ovens built by farmers during his administration. The sulphur emissions cut the grain harvest by 70 per cent. "The forest disappeared. The grass stopped growing. It was like the area had undergone an atomic bomb explosion," one resident was quoted as saying. As many as 1,360 coke ovens were built; the provincial government is still trying to close them down today.

Hu next took charge of Tibet, China's most sensitive regional posting and a test of any official's mettle. He kept a low profile for much of his time there, partly because, like many Chinese officials, he could not adapt to the thin air and spent long periods back in Beijing, recovering from altitude sickness. But he left his mark on the fringes of the Chinese empire, declaring martial law and jailing hundreds of monks after anti-Beijing protests broke out in 1987. He had arrived in Tibet after a period of relatively liberal rule, instituted by Hu Yaobang, who had tried to make room for Tibetan culture and language after the destruction of cultural revolution, but, according to Robert Barnett, at Columbia University, he ran a "very tough regime".

Still, Barnett says, his reign was better than what came next. "He didn't try to dismantle an entire apparatus of tolerance that had been developed under Hu Yaobang in the 1980s." Rather, Barnett believes Hu is most at fault for picking the people that followed him. "They were very aggressive; very hard line, [using] very old-school ways of handling barbarians at the frontiers. Crack down on their rituals, be very wary of intellectuals. Rein in their religion."

Soon after returning to Beijing, Hu was singled out, at an extraordinarily young age for modern Chinese leaders, as a future party secretary. In 1992, at 49, he was appointed to the top leadership's inner-circle, known as the "standing committee of the politburo", effectively putting him in line for the top job 10 years later. The clarity that once marked his place in the "liberal" camp started to cloud over.

Hu has kept everyone guessing since then. One Chinese commentator compared his policy pronouncements to a duck walking with one foot pointed to the left, and the other to the right, maintaining an ungainly ideological balance which looks unstable from a distance. China itself has struggled with the same balancing act, between a market economy and a one-party state, for the past three decades.

Since 2002, Hu the "reformer" has allowed the privatisation of large sections of the Chinese economy and the listing of state companies overseas. As head of the party central school in Beijing, he backed debate and study of democracy and encouraged the development of the internet. As a result, Chinese individuals and companies are freer than ever to travel overseas, buy homes and cars and do business. Despite the sensitivity of religion, Hu even held an international conference to promote Buddhism in 2006.

And yet the same Hu has presided over a significant tightening of the media, the jailing of journalists and a concerted campaign against "neo-liberalism" in economic policy-making and "spiritual pollution" on the internet. Large parts of the economy have been sealed off from foreign control as "pillar industries" and entrepreneurs have been attacked for stealing "state assets". To the horror of many in China, Hu praised Stalinist North Korea in an internal speech early in his first term. And while promoting Buddhism, China has continued to pillory the Dalai Lama.

Hu's "left-foot, right-foot" policy waddle is a recipe for paralysis, according to its critics. "This government is very democratic. They listen to everyone," a Peking university professor says sardonically. "This would never have happened under Zhu Rongji [the previous premier]. He would have just made a decision."

Hu consults widely, but more selectively than his predecessors. Chief executives from large multinationals, who could previously be sure of an appointment with the president or premier, have mostly been shunned. Instead, Hu prefers photo-opportunities with coal miners, farmers and migrant workers. Foreign CEOs and rich Chinese do not fit the political narrative that Hu has sought to construct for his administration, of closing the gaping fissures that have been opened by China's robber-baron capitalism - clefts between the rich and poor, the coast and the hinterland, the cities and the countryside.

Hu's campaign to close such gaps, and build what he calls a "harmonious society", resonates with large sections of the population, as well as with his own governing experiences in Gansu and Guizhou. But his adamant belief in single-party rule, coupled with his distrust of the private sector, has enraged and disappointed the many professionals and intellectuals who expected a more modern leader. "He has no deep understanding of the meaning of democracy and freedom," a Peking university professor tells me.

Few global leaders face challenges of the dimensions that Hu does, of governing a vast, fractious nation which is compressing into a few decades the industrial revolution that took a century in countries such as the US and the UK, with none of the pressure valves that a democratic system provides. Chinese pride binds the nation together, but so does another, largely unspoken, fragile compact: that if you play by the party's rules, then you and your family can get rich.

Ding Xueliang, who is based in Beijing for the Carnegie Endowment for International Peace, says foreign views of Hu have been too easily framed by the fact that he grew up in a radical time, with no overseas experience, making him "a kind of Chernenko" - a symbol of an unworldy, Communist party apparatchik, with no distinctive political personality.

Ding says this underestimates how Hu himself has been inevitably shaped by the times. "Hu has some strongly held views, but he is a practical person. China today is so completely integrated into the outside world - and the outside world is capitalist. If he wants to develop his country he has to make his way in a global capitalist system. Hu has no other choice."

Even after five years in office, it may be too early to judge Hu. He has been going about gaining control of the apparatus of bureaucracy in familiar style, quietly, remorselessly, like a silkworm eating through a leaf, in the words of one senior official. In his second term, he should have a far freer hand. So topsy-turvy is Chinese politics that Hu may have only genuinely consolidated power by the time he steps down from office in 2012.

By then, the world, and perhaps even the Chinese themselves, might have a better idea of who he is, what he believes in and what his country - which by then will be breathing down the neck of the US as a political and economic competitor - really stands for.

Richard McGregor is the FT's Beijing bureau chief.