A mild-mannered, quietly spoken, bookish man who converted to Buddhism in his twenties, he did not set out to become a radical. To those who know him, he was just a public-spirited and single-minded young man who was dedicated to helping others and advancing his country.

An interview published in state newspaper China Youth Daily in 2001 portrayed him as a 'quiet, gentle, courteous and humble' 27-year-old volunteer so devoted to his environmental protection work that his girlfriend ditched him for not having a proper job.

'He should be an example for our young people,' the article said.

Less than seven years later, this exemplary young man was jailed for 'inciting subversion of state sovereignty' by posting articles on the internet on rights abuses and speaking to foreign reporters. His attempts to help other activists in trouble and to connect them with the media proved too much of a challenge to the ruling Communist Party's authority.

In interviews in the months before he was arrested, Hu talked of what compelled him to take up rights activities.

Born in 1973 in Beijing, Hu was the son of political outcasts. His parents, graduates of elite universities, were sent to labour in the countryside after being castigated as 'rightists' in 1957 along with other intellectuals who had criticised the government.

He was separated from his mother at a young age after she was sent to work away from home and the family was not reunited until he was five, when his parents were vindicated. It was a lonely childhood - and one that instilled in Hu a sense of solidarity and sympathy towards those who are marginalised in society.

As a young child, he already understood discrimination. Once, he was barred from performing on stage when teachers found out he was a son of 'rightists'.

'We were all made up and ready to get onto the stage, then someone muttered, 'This child's parents are rightists.' And the teachers stopped me from going,' he reminisced.

'Because my parents were branded rightists, not many children wanted to play with me. I was an outcast, that's why I feel for HIV/Aids patients,' he said. 'I would play with other 'friends' like birds, beetles, flowers, grass and trees. They would always be there for me when I was lonely. And I felt their lives should be equally respected.'

In 2001 he met veteran Aids activist Wan Yanhai , who introduced him to the plight of people who had contracted the deadly disease via illegal blood sales in impoverished villages in Henan province.

He also worked with Dr Gao Yaojie , the whistle-blower on the mainland's HIV/Aids epidemic, helping the elderly doctor liaise with journalists before the government formally admitted there was a problem. Unable to deal with incessant official harassment, Wan and Gao fled to the United States.

But it was Hu's activism beyond health issues that alarmed the government.

In April 2004, he placed 15 yellow roses in Tiananmen Square to commemorate the 15th anniversary of the death of former Communist Party chief Hu Yaobang .

The reformist leader's death in April 1989 prompted many students to pay tribute at the square, sparking mass demonstrations that ended in the June 4 crackdown.

Indignant at government harassment and detention of fellow activists in the following years, Hu started acting as their campaigner, spreading word of their ordeals by contacting overseas rights groups and journalists.

Hu played an important role in drawing attention to the plights of activists such as Gao Zhisheng , Guo Feixiong and Chen Guangcheng , all of whom ended up in jail. (No one knows Gao's whereabouts now. Guo is still in jail and Chen remains in extrajudicial detention after his release in September.)

As a result, the authorities stepped up harassment of him and his wife, Zeng Jinyan . They were under constant police surveillance and he was from time to time detained at undisclosed locations. He disappeared for 41 days in February 2006 after he joined in a hunger strike in support of fellow activists. Even after he was released, he was still confined to his home most of the time, up until his arrest.

'I didn't choose to be their spokesman, but in the end I was the only one left. Then you realise you have to persevere,' he said in a 2007 interview. 'I felt compelled to protect these pillars of our society. This is one duty I can fulfil for this country. The only way you can stop me from speaking out is to kidnap me, or put me in jail.'

Soon after speaking those words, he was put under a long period of house arrest until he was officially arrested in December 2007 - his daughter was just one month old at the time. Five months later he was sentenced after a one-day trial.

The punishment extended to his wife and young daughter even after Hu was jailed - they continued to live under police surveillance and harassment. Zeng was taken out of Beijing during the 2008 Olympic Games and her movements are still closely monitored now.

In April, she moved from Beijing to Shenzhen with her three-year-old daughter in search of less harassment and in the hope Hu could join them after his release.

Since Hu was jailed, she had largely avoided contact with the media, as a condition for continued access to her husband, but broke her silence two weeks ago when her landlady in Shenzhen tried to evict her, citing official pressure.

'Step by step, I have been forced into a corner - if there is no room for survival, of course I have to resist,' she told reporters at a lunch she organised for supporters in Shenzhen.

She said she had mixed feelings about Hu's imminent release. She hopes her husband, who suffers from chronic hepatitis B, can get better medical treatment after his release but also knows the authorities will most likely put them both under house arrest again.

Earlier this year, she said on Twitter that Hu expected to be 'put in a big prison after his release from the small prison'.

She recently said Hu was keen on resuming his rights work after his release, but also knew he would be constrained by 'the deprivation of political rights', which will prevent him from engaging in activism and talking to the media for at least a year.

'He really wants to get back to his work - but it's not possible to enjoy things like the freedom of speech, assembly and publication,' Zeng said.

Her dilemma is that she wants the family to be reunited but also desperately wants their daughter to avoid being confined to home with them.

For the time being, she has put her child into the care of relatives but worries that she and Hu may not be able to see her for a long time.

'No doubt I can't wait to see him ... but if they really put us under house arrest, we won't be able to look after our child. She is too young [to be separated from us],' she sighed. 'But there is little we can do.'

From the moment they found out she was pregnant, she said, Hu started worrying about how their future child would cope with the constant surveillance and harassment.

'He worried that she would end up like Gao Zhisheng's daughter,' Zeng said. Gao's daughter, who used to confide in Hu, was often followed by security agents at school and had been beaten by people who monitored her. She now lives in exile in the US but still suffers from depression.

Jean-Philippe Beja, a senior research fellow at the Centre for International Studies and Research at Sciences Po in Paris, said Hu had 'crossed the invisible line' in the government's eyes and had paid a heavy price for being a well-known activist.

'His way of advocating made him a target of government anger: he talks to the Western media and inside China he has become a kind of a standard bearer in the rights movement,' he said.

'When you become a symbol, on one hand you're protected, but on the other hand, it's very dangerous.'

The tragedy is that Hu, who started out as a passionate young man wanting to do only good for society, came to be seen as an enemy of the state, was jailed and is now unlikely to enjoy genuine freedom even upon his release, rights groups say.

'It reflects a profound distrust of the party towards its people. They think it's too dangerous for people to contribute towards society,' said Nicholas Bequelin, senior researcher for Human Rights Watch.

Road to rights

1973 Born in Beijing

1996 Graduates from the Beijing School of Economics (now Capital University of Economics and Trade), where he majored in information engineering

1996 Joins Friends of Nature, one of the mainland's oldest environmental NGOs, and starts environmental protection work

1998 Works on saving wild elk and Tibetan antelope

2000 Begins to be involved in Aids prevention work

2004 Founds Beijing-based Loving Source, an Aids prevention NGO

2005 Participates in anti-Japanese demonstrations over Diaoyu Islands

2006 Marries Zeng Jinyan, with whom he has a daughter in 2007

February 2006 Vanishes for 41 days while his wife posts a blog detailing his disappearance

May 2007 Attacked on his way to a market by people who he claims to be 'secret police'

December 30, 2007 Arrested for subversion

April 3, 2008 Sentenced to three-and-a-half years in prison, with one year's deprivation of political rights, for his articles published on foreign websites and interview with foreign media

2008 Nominated for Nobel Peace prize

December 2008 Awarded Sakharov Prize for Freedom of Thought by the European Parliament