At first, Chung's enduring image - one of glamour built on an impressive range of film roles in the 1980s - appears at odds with her commitment to environmental protection. She is keen to point out, however, that she has spent more time working for local green organisations (13 years) than she did making movies (11 years, book-ended by Johnnie To Kei-fung's The Enigmatic Case in 1980 and Ann Hui On-wah's Zodiac Killers in 1991).

Chung, 46, seems to have disowned her glamorous former self. She sounds clinical when articulating her frustrations concerning the shackles of stardom and the bad films she was forced to make at the pinnacle of her career. When the conversation turns to urban regeneration and nature conservation, however, she comes alive, describing the government as 'primitive' for closing Oil Street's arts village and Wedding Card Street (Lee Tung Street). The fencing in of willow trees in the Yung Shue Tau garden on Temple Street brings her close to tears. 'With the roots fenced in, the trees can't even breathe,' she says.

Chung's latest cause has taken her to the rural hinterlands of Shaanxi province, where she has visited villages in which farmers - mostly women who have been left to tend the fields while their husbands work in the cities - are testing a biogas project: animal waste is processed to produce methane, which is used to generate electricity for both cooking and lighting. Known as the Sunflower Project, the programme is organised by the Shaanxi Mothers Environmental Protection Volunteer Association and has provided power to 1,144 households in 26 villages since it was launched in 1999.

'I never thought they could do such a hi-tech thing with such low-tech means,' says Chung, who travelled to Shaanxi in November under the auspices of Hong Kong environmental organisation Friends of the Earth (FoE). 'I have the utmost respect for the several organisations that have made it happen - they are labouring for the cause silently. And [the villages] are not doing it only for themselves; they are campaigning for more units so more people can benefit. It is a great achievement.'

People such as Wang Ming-ying, a veteran community organiser who has worked tirelessly on

the project for six years, remain largely anonymous, while Chung has been installed as its public champion. 'I think I can help by encouraging more people to believe the plan works. If they are to further their project, they have to get more people to support them,' says Chung. 'It's up to us to make more noise for them. From [Shaanxi], we hope the project will spread to other parts of the country.'

Chung is a dedicated supporter of FoE and its director, Mei Ng Fong Siu-mei. Readers may recall images of Chung counting smoky vehicles with the organisation's volunteers in Ngau Tau Kok in 1993. She has served for many years as the body's 'green ambassador' and has been placed strategically in media campaigns concerned with everything from saving plastic bags to planting trees. In 2002, she spearheaded a campaign aimed at teaching children the value of nature by allowing FoE to make Christmas cards with photographs she had taken.

Ng, who was the architect behind Chung's induction into FoE in 1993, is keenly aware of the actress' effectiveness in furthering her cause. 'We know Cherie wants to keep a low profile about what she does,' says Ng. 'But we need her to make our work visible. And she's kind enough to lend us help on that.'

Media attention, Chung says, is something she would rather avoid these days. 'I had this struggle inside me before I agreed to come on board this project - but if I wasn't going to secure exposure for the project, why should I have been involved at all? Anyone could have gone on the trip in that case.'

Skirmishes with the tabloid press have taken a heavy toll. Reports about her financial affairs left Chung seething and axe-grinding reporters from the entertainment pages interpreted her ensuing silence as arrogance. 'I've accepted they behave like this - probably that's why we just don't click and I don't ever want to face them again,' she says. 'Sometimes, when I was interviewed by low-calibre people, I got really mad. I was disgruntled that I was expected to agree to their stupid, low-level thinking.'

Chung says she was astounded by the rise of the paparazzi in Hong Kong - a development that vindicated her decision to quit the entertainment industry while she still had an untarnished reputation. '[All] I miss about being in the film industry is the creativity that goes into the production process,' she says. 'After I left the scene, I felt my life had been enriched - I felt much happier and I learned so many things I wouldn't have been able to if I had still been an actress.

'When everybody tries to gossip about you, you tend to seal yourself off - and bit by bit you lose touch with the outside world. That's why I decided I had to leave it all behind - I even left Hong Kong for a while, to get some space. When you're in [the business] you have people around you, holding you and taking care of you. Some people enjoy that - and all the best to them - but it's not for me.'

Chung's decision to retire from filmmaking in 1991 raised many eyebrows; she was just 31 and the popularity she had won with award-winning work in the 80s - she was nominated for Hong Kong Film Awards for performances in The Story of Woo Viet (1981), Hong Kong, Hong Kong (1983) and An Autumn's Tale (1987) - remained high. A survey of her filmography, however, reveals her participation in an increasing number of flops as the 80s drew to an end; she starred in no less than 23 films between 1987 and 1989, many of which, Chung says, are better left forgotten.

'I was just sick and tired of the film scene,' she says. 'I was quite popular and people forced me to make movies I didn't want to. There were a lot of gangsters back then ... then again, human beings are never allowed to live completely in accordance with their wishes, so there you go.'

In 1979, Chung entered the Miss Hong Kong pageant 'for fun' and came fourth. Her subsequent career as an actress didn't really ignite until The Story of Woo Viet, in which she played a desperate Vietnamese refugee who escapes from a camp in Hong Kong only to be sold into the flesh trade in the Philippines.

Her star continued to rise with Hong Kong, Hong Kong, in which she played an innocent illegal immigrant from the mainland caught between a marriage of convenience to an elderly carpenter (Kwan Hoi-shan) and a passionate affair with a boxer (Alex Man Chi-leung). The early 80s saw Chung typecast as a sex kitten, a trend put paid to by intense performances in serious dramatic pieces such as Tsui Hark's Peking Opera Blues (1986) and, most importantly, Mabel Cheung Yuen-ting's An Autumn's Tale, in which Chung starred as a young student who is spurned by an adulterous boyfriend (Danny Chan Pak-keung) before falling into a subtle romance with his loud cousin (Chow Yun-fat).

The 80s - a decade of feverish activity for Hong Kong's film industry - may have generated big money for actors such as Chung, but the price was intense pressure. 'I was only sleeping two to three hours a night and I didn't even have time to go to the doctor's. What I did also became a production line - that's when I decided I had to find an alternative way of living,' she says. 'I just felt that it wasn't fun anymore. If I could have found films that interested me, then maybe my career would have been prolonged for a bit. But as I was not making movies I liked, there was no point wasting my time.

'I can't deny I still love films - they have given me so much experience in life and a feel for places and cultures far away; customs and traditions that I wouldn't have known of otherwise. Films gave me a lot of the knowledge I have now, all the stuff about photography and music. It broadened my world.'

In the tradition of many a retired actor, Chung is pursuing a career as a photographer; her work in the mainland for charity causes has resulted in exhibitions, the photographic documentation calling attention to campaigns that would otherwise have remained anonymous. It's a job someone has to do, Chung says, ever reluctantly.

'I enjoyed that trip to Shaanxi,' she says. 'Some of the people confessed they didn't know me and I enjoyed that feeling of freedom. That's exactly what I looked for when quitting movies so early in my life - I don't want people to know me, I want to rediscover my own life. I don't want to live my life concerned about how people see me.'