During the probate hearing in May, Ian Mill QC, for Chan, identified Chang as the person who had provided a document relating to the deal in which disgraced former lawmaker Gilbert Leung Kam-ho bought the land back from Wang's company, Chinachem, at the price he sold it 20 years earlier. The document was used to attack testimony of Leung, a key witness for the foundation.

In the judgment, Poon agreed with Chang's barrister Ronny Tong Ka-wah that the privilege must have been waived at the hearing in May when Mill told the probate judge, Mr Justice Johnson Lam Man-hon, in open court that the source of the document was 'Edmond Tsang'.

'It does not lie in Mr Chan's mouth now to say the identity of the true informant should be kept confidential by privilege,' the judge said.

Poon also disagreed with Jonathan Harris SC, for Chan, that no substantial benefit would be gained by a disclosure order because Chan had agreed to clarify the matter and to place a correction notice in the media to clear Chang's name.

The judge said such a notice was simply insufficient for a 'supposedly innocent person who had unwittingly become involved in a tortuous act'.

Chang, a securities and property investment professional, said that he had never been a source for Chan or his legal team and he had been called a 'traitor' or 'backstabber' by friends and colleagues because they thought he had supported Chan.

In yesterday's judgment, Poon said Chang had reasonable grounds to proceed with his libel claim arising from the news reports of Mill's address in open court.

In a statement released through his public relations agent, Chan said he respected the decision and he would not appeal.

Tong said Chan's lawyers now had to provide information on the informant's identity to Chang's legal team within 14 days. That would include the informant's name, address and contact information, he said.

In a telephone interview yesterday, Chang said he would pursue a claim of defamation against the informant after obtaining the details from Chan's lawyers.

He said he welcomed yesterday's judgment and hoped he could be provided with the information as soon as possible. 'I am innocent and should not have been dragged into the probate dispute of others. It is an unhappy experience for me.'

He said he usually did not want to have a high profile. 'But the matter is so serious that it forces me to litigate. I don't really want to do it but I felt compelled to talk about this publicly,' Chang said.

Noting that his barrister had suggested earlier in court that the mistake could in fact have been 'by design', Chang said: 'Perhaps that person made a wrong estimate about me and expected there would be no consequence following the incident because I might not come out and talk about it. But I feel I have to clear my name this time.'

Chang said he remembered meeting Chan only once in 1993, when Leung introduced him as his fung shui master.

'I don't believe in fung shui. I could not say I have any impression about [Chan]. We have different interests and opinions,' he said.

The foundation's solicitor, Keith Ho Man-kei, said he did not see the ruling having any impact on the probate case.