The last time he had seen a picture of Teddy Wang and noticed Nina Wang was still receiving his calls was 'after the year 2000 and some time before she died', he said without being specific about the dates.

The first time he heard Teddy Wang's voice on the telephone was a few years after the abduction, he said, again without being specific or giving details of the conversation.

'That time Wang used a speaker, so I could hear his voice,' he said. 'He mentioned Wang's private nickname in the conversation, so we knew it was him.'

He said he was bound by a written agreement he had made with his late boss to keep searching for her lost husband until 2015, even though Teddy Wang was officially declared dead in September, 1999.

'I made a promise to Wang that I wouldn't stop no matter whether I had succeeded or not by then,' Mr Wong said. 'We had a written agreement and therefore I won't stop searching.'

He refused to disclose the date or the contents of the agreement.

Mr Wong said a team had been set up 19 years ago to search for Teddy Wang which was still operating, although its numbers had dwindled because of limited funds since Nina Wang's death.

'Our team used to have a lot of members, but now we only have 10,' Mr Wong said. 'They include retired Hong Kong policemen, private detectives and bodyguards of different nationalities. All the funding comes from my own pocket.'

In their quest they had travelled to many countries, including in Europe and Asia and the United States, meeting Teddy Wang's convicted kidnappers and related parties as recently as this year.

Asked if he had faith in succeeding in the search, Mr Wong said: 'I don't dare to say. After all, it's been 19 years... but no matter what, I will dig out the truth and at least know where Teddy Wang could be. I will get an answer.'

Mr Wong said he would not comment on the probate case between Chinachem and fung shui master Tony Chan Chun-chuen, except to say: 'I believe the judicial system is fair and independent.'

He said the first time he had heard of Mr Chan was April 7, 2007 - four days after Nina Wang's death.

And the first time he had heard of the 2006 will - which Mr Chan says supersedes a 2002 will and leaves Wang's fortune to him - was a day earlier.

'A lawyer whom I knew contacted me and told me that the estate would be controlled by an individual person,' Mr Wong said.

'Then on the following day, they sent us a fax saying briefly there was a person named Tony Chan who would take up the estate... This was the first time that I knew of such a person. I had never heard Wang talk about him before.'

He was also 'a bit shocked' to learn of the possibility of another lawsuit following on the heels of the decade-long battle fought between Wang and her father-in-law, Wang Din-shin, over the estate.

'My first reaction was: 'What, again?',' he said. 'But from day one when we received the fax, we had already decided to fight this battle. We wouldn't run away from it.'

Asked if he had confidence in the outcome of the case, he said: 'All company staff, Wang's family, friends and I all shared a common belief; that was to help Wang to complete her wish by devoting her estate to charitable business.'

Mr Wong also refused to say whether he would show up on the first day of the Wang probate hearing in the Court of First Instance next Monday.