Once in Hong Kong he made contact with the same Yellow Bird officials who, in 1989, helped Tiananmen Square organisers such as Wu'erkaixi and Chai Ling flee abroad in the tense weeks after the June 4 crackdown.

Although the organisation had scaled down its operation, officials were still able to put Mr Zhang in a safe house. He is now on his way to another country.

Yellow Bird is currently looking after six activists who are in Hong Kong awaiting asylum in a third country.

Using a system of mainland sympathisers, who operated at great personal risk, the movement managed to slip some of the most wanted student leaders out of the country.

It has never revealed its methods in case further problems in China meant the ''railroad'' would be put into full use again.

''After five years, I think all Chinese people in Hong Kong are still thinking about Tiananmen Square,'' one of the organisers said.

''I think they are very concerned about what will happen because in three years we are united.'' He said the number of dissidents leaving China has dropped over the last year, and that many were being encouraged to stay.

''After five years, many people still want to come out but we advise them to stay . . . we need them inside to bring about a new kind of China.'' Since Yellow Bird was formed, it has helped 500 dissidents flee from the mainland. And it supports people like Mr Zhang, who was wanted in every province for trying to expose high level corruption and for escaping from an education centre although he hadnever been convicted of a crime.

''I did not intend to link my personal ordeal with politics at first, but what I experienced during this period made me understand the fundamental problem is the system of the country,'' Mr Zhang said.

During a seven-month stay in an ''education centre'' on the other side of the Lowu border fence, Mr Zhang documented unconvicted ''prisoners'' making rice noodles for export to the United States in filthy conditions.

His comments on the abuse of power in the legal system in Shenzhen has given the first real insight into an otherwise closed part of the society.

''China has laws but no one wants to carry them out,'' Mr Zhang said.

''I went to Shenzhen because it is an open place with good prospects. My decision was not wrong. Shenzhen is a good place and there are a lot of chances but it is the people inside it who are corrupt who disappoint me.'' Mr Zhang's problems began in 1990 when he tried to divorce his wife who did not want the separation. He now believes she had formed some sort of relationship with a senior court official.

Soon afterwards, he said, the official ''lost face'' when Mr Zhang saw him and his wife in the official's car outside the Shenzhen Middle People's Court.

Three days later the official, who Mr Zhang said was a powerful man, had him ''unlawfully detained'' for three days in a room at the court building.

''Twenty-five days later they held me again for three days. They had no right to arrest me and were abusing their power,'' he said.

But his real problems began in 1992, after a court clerk allegedly found that the senior court official had accepted a bribe - said to have been paid in US dollars - during a multi-million fraud trial involving a Shenzhen company.

Mr Zhang, who was first employed as a judge by Shenzhen city in 1988 handling mid-level commercial cases, said the manager of the company later left China for Singapore.

''I then wrote to a lot of the upper level judges and to the central authorities, including Li Peng, complaining about the case but I never received any response,'' he said.

In all, Mr Zhang wrote about 300 letters over the next two years to senior government officials asking for help and seeking an investigation into his detention.

But in April last year he was grabbed by Public Security Bureau (PSB) officers at his house and taken to the Shenzhen Labour Education Centre on Shang Bu Bei Road.

As soon as he arrived he was punched and kicked by five members of staff, a beating he believed seriously damaged some internal organs. All of his attempts to have an appeal heard went unanswered.

''Finally a judge from the Guangdong High Court came to see me and promised to help,'' Mr Zhang said.

''But then he said I was making a lot of trouble between government departments and that I had a light sentence at the moment, but if I continued I would get a longer one.

''On September 1 last year, because I kept writing letters, the chief judge and three sub-chief judges came to see me to sort out the problem peacefully.'' They told Mr Zhang if he did not agree to sign a ''contract'' binding him to stop pursuing the matter, he would be held in solitary confinement normally reserved for violent criminals.

When he again refused to comply, he said guards at the centre started going through his possessions and he found himself given harder tasks and told to work longer hours.

During his seven months at the centre he saw inmates blinded and made deaf by beatings.

He also witnessed young inmates making rice noodles for export to the US in rooms where hygiene conditions were ''dreadful''.

Then, last November, he had an accident while working on the printing press when one eye was flooded with ink.

''The authorities allowed me to go out for treatment and when I got to the Shenzhen People's Armed Police Hospital, I fled.

''The same night I bought a plane ticket to Beijing and went to the US Embassy but I couldn't get in because of the army guards outside.'' He said he kept trying to hand over his evidence but was followed, and every time he made a telephone call the line was tapped.

Earlier this year he slipped into Hong Kong using a false name while part of a seven-day tour of the territory.