'I believe what I am most devoted to is free writing, with no political right or wrong about it,' he says. 'Other writers might have stopped their writing because of this reason, but I wouldn't. I will continue my writing even if my writing will have to be held in the drawer for future publication. I just hope that in the near future these writings will be able to come to the world.'

During rehearsals for Margin Upstairs, he says, the authorities went through the scripts well after midnight and decided that it should not be publicly performed in state-run theatres. Members of the city government called an urgent meeting and warned the major newspapers and TV channels against publicising the show. But word of mouth helped make the production a success in underground venues.

'After the commercial success of the play Margin Upstairs, I decided to make it into a movie and we went to Beijing, but some people in Shanghai informed the authorities in the National Security Bureau and so the National Broadcasting and Television stopped this from being filmed,' he says. 'So, from that time, I know some people have their eye on me and keep watching me and my activities.'

Lately, he's been tilting at the windmills in a new way - by practising a freeform, improvisational style of playwriting on the internet.

'The present dramatic forms I am practising now could be summed up with a sentence like 'I am crazy, therefore I am',' he says, flipping the Descartes cliche on its head. It is a play without a name and without an ending, he says, simply a gradual connection of his remarks, comments and writing that build into a play - or maybe not even a play at all. He prefers to call it only a 'great live event'.

'This play is sort of controversial because if I announce it is a play, I don't have a licence for this,' he says with a laugh. 'If I don't announce this as a play, it is just people gathering together in my web place. But then it might be considered as public speech, and this might be forbidden by the authorities. But I could also announce I had been out of my mind and that I had a family history of madness, but this all depends on the readers' reception of the ideas and they could derive the ending of the play themselves.'

While he doesn't consider himself political, Zhang is known as a political playwright because so many of his plays have not been performed due to censors. It is the source of his life's frustrations he says, to produce plays in such as closely guarded political climate. Yet he also says he never cares whether these plays would see the hot stage lights of the theatres. His latest play, Raped Anti (as in the Greek Antigone), has been accepted for publication in Shanghai, but another work, The Jar Players, has been forbidden.

'In the past decade, my works have been gradually coming out, so it isn't that my works aren't being published at all,' he says. 'I have one or two published at one time and one or two censored at the same time.'

Now 49, Zhang takes on a much more pragmatic air than he once did. In between writing his plays, which may or may not ever be performed, he makes a living by writing screenplays and TV scripts, as well as directing, designing and working in the theatres of Shanghai.

'In Chinese tradition, people were not afraid of new voices, because the whole society was not controlled, so they were not afraid of individuals,' he says. 'Now they are afraid of true voices which would disturb or deconstruct the line of the authorities, so that is why they have strict control of the internet, newspapers, and things like this. Especially the web.'

Zhang's screenplay for Those Left Behind won the best film at the 16th Cairo International Film Festival, and he also spent nearly a year in New York under a fellowship from the Asian Cultural Council. To balance his need to write openly about topics which interest him while also making a living, Zhang works with and develops civilian theatre in Shanghai.

'In China, there are these little or petty civil people, there is no normal, large or great civil people,' he says. 'What is civil is very much despised, or condemned, so the civil tone is despised in the city as well. What I consider as 'civil' is just the basic identity of common people in China, as a republic. The concept of a people is very susceptible, for example, in the feudal ages, the idea of people was represented by the ruling class, the kings and the emperors. In democracy the idea of the civil is most important. But in Chinese society, what is called civil society and civil rights do not exist at all. My civil plays attempt to restore this kind of normal identity to the common people.'

Much of Zhang's pragmatism as well as rebellion comes from his background. At the start of the Cultural Revolution, Zhang's family became targets of the Red Guard and he was exiled to Yunan, where he began to read and write privately, developing his tendency to write for the simple act of creation. In 1978, he passed entrance exams to study at Shanghai's drama academy, but after a few years in school he was jailed and sent back to Yunan to work in a sweater factory. It was here that he once again turned to his 'closet literature'. Later censorship molded his work into the form of 'fable plays' and 'underground plays'.

'This was a time of even more strict censorship, so all my work had to be written in the form of the fable. For me, these plays are not in a specific time period. Right now I'm still writing these types of plays.'

Over the past 20 years, Zhang Xian has seen a number of wenyi ('spring of art') - or defrosting of censorship and state controls - come and go, lasting only a year or two before freezing solid for another decade. Artists and writers become excited at the onset, he says, then begin to feel the pressure behind them as the authorities become wary of the restrictions they have loosened.

Late last year and early this year was supposed to be a new spring. A large number of plays about morality, love and sexual life appeared, but have suddenly been cut off, including a reproduction of the Vagina Monologues.

'Because of the strict national control, the theatres have declined seriously and extremely, so some people are trying to save the theatre from this situation,' he says.

Recently, the government initiated a new reform among the state-run theatres and cut subsidies, letting them become financially independent and setting the theatrical boat adrift in Shanghai.