Testifying through a video link from a Singapore court, Tay Eng Hseon told the Court of First Instance that by October 9 that year Wang's condition was "on the verge of becoming bad" and she could have collapsed at any time.

Professor Tay, a former senior consultant and certified oncologist at KK Women's and Children's Hospital, said he believed at the time that Wang could not beat the disease, despite being "determined to try everything to survive".

The contested will that fung shui master Tony Chan Chun-chuen claims leaves him the entire Chinachem empire was signed on October 16, 2006. His rival in the probate battle, Chinachem Charitable Foundation, is relying on a will signed in 2002.

The doctor, who treated Wang for almost a year, said that during her last admission to the hospital, between October 4 and 11, 2006, her condition had fluctuated and deteriorated so much that she had had to postpone her return to Hong Kong.

She had been due for discharge on October 9 but he refused to discharge her because she had abdominal discomfort and an intestinal obstruction and had vomited. Between September and October, he said, Wang had lost 9kg.

Professor Tay said that in a discussion in September with Wang and her sister Molly Gong Chung-sum, he had offered her three options, including a non-treatment method known as "supportive care". But Wang, whom Professor Tay described as a "fighter", did not choose to switch to a less aggressive treatment.

Reciting from medical notes, he said Wang's condition had been quite good in July 2006 and she had been able to walk.

But in August she started to feel weak, breathless and lethargic, and required a wheelchair at the airport and hospital. By then, he said, Wang appeared to be "a different patient", with her condition much worse than in April of that year.

Concerning Wang's mental condition, Professor Tay said he could not tell if she suffered from delirium but he believed her cancer had caused an overall disturbance to her basic functions and fatigue had affected her concentration and consciousness.

Another Singaporean doctor, Tan Yew Oo, also testifying through the video link, said the cancer drugs Wang used were not associated with mental abnormality or delirium.

The court yesterday also heard evidence from another Singapore witness, Thomas Chan, a Goldman Sachs managing director in private wealth management, who had handled substantial share transactions for Wang since the 1990s.

The broker said he had helped Wang in late March and early April 2007 to buy £30 million (HK$383 million) of shares in RCG Holdings - a company she had invested in with Tony Chan.

He told the court he obtained oral confirmation from Wang by telephone on April 2 - a day before her death - that she was happy with the transaction.

However, he said he had no recording of any telephone conversations he had with Wang between February and April regarding the purchase, even though his company had a policy to record clients' orders, because the conversations had taken place on his mobile phone.

The witness said he was shocked when he learned about his client's death from the media because he had not realised how ill she was.

The hearing before Mr Justice Johnson Lam Man-hon continues today, with members of Tony Chan's family expected to testify. — SCMP