On July 17, 2000, she shouted on the doorstep of vice-chancellor Cheng Yiu-chung, calling on him to step down for allegedly pressuring Dr Chung to stop conducting popularity polls on then-chief executive Tung Chee-hwa and the government.

Two months later, he and his deputy, Wong Siu-lun, resigned after an independent inquiry found the accusation valid.

'As the president at that time, I felt I had great responsibility to lead other students,' said the former politics major. 'It was kind of media training in reality. I had lots of interviews, but my words were often misinterpreted. So I had to keep making clarifications ... And I have realised the huge impact of the media.'

She believes she could have done one thing better. 'After the polling row, I should have motivated more students to discuss academic freedom when the new term began.'

Ms Chang said she had been very 'well-behaved' in secondary school, but 'tertiary education was the turning point of my life'.

In 1997, she wanted to get into the University of Hong Kong after watching students on television fighting to erect the Pillar of Shame, which commemorates the 1989 Tiananmen crackdown, on campus.

'I was desperate to meet the students' union committee members at that time,' she said. 'The June 4 crackdown had a great impact on me. I thought [the central government] was high-handed and conservative,' said Ms Chang, who was then a primary student.

Now, as a Greenpeace campaigner, she said she was trying to view the mainland from another perspective. 'I often visit some poor rural areas on the mainland to see their development,' she said. 'The room for people's political involvement still needs much improvement ... [But] since they have a large population, they really care about people's livelihood for fear of uprisings.'

After finishing her master's degree in development studies in Britain, Ms Chang joined the Democratic Development Network in 2002 and then switched to Greenpeace in 2003.

'Political or environmental issues are just a cut-in or trigger point. What I want is to promote civil society and help citizens be empowered,' she said. 'The most disadvantaged should strive to protect their fundamental rights.

Greenpeace China, established in Hong Kong, is celebrating its first 10 years. Ms Chang said initially, the biggest challenge was how to adapt conventional Greenpeace campaign strategies to local society.

'We use lots of gimmickry elsewhere, but it is not easy to make it work in Hong Kong,' she said. 'We don't want to be seen as a troublemaker and wish to open a dialogue with the government.'

Ms Chang said she had never been fearful in her activism. 'Even when I came across the university's high-ranking officers afterwards, I was not embarrassed or intimidated,' she said. 'There is nothing to fear as long as I am confident in what I say. We just need to respect each other and be open to ideas.'