According to court documents, under an arrangement the father made in 2004, Vivien and her sister Angela would each receive HK$4.5 billion after his death. However, they would each have to transfer HK$1.5 billion to the mother, so they would get HK$3 billion per person.

Yang claimed the arrangement meant Vivien should transfer to her a third of the market value of the properties that the daughter received, which the court heard was worth "substantially more than HK$1.5 billion".

Initially, the mother agreed to take HK$1.5 billion in cash instead of a one-third entitlement. She later cancelled the agreement on the grounds that Vivien had misinterpreted the arrangement, exerted undue influence or breached her fiduciary duty.

Vivien took over control of Nan Fung after her father was diagnosed with Alzheimer's disease in 2009.

Details of her mother's claim were revealed in yesterday's judgment, in which Angela was allowed access to documents in Vivien's possession containing family arrangements made among the father and daughters.

Ms Justice Bebe Chu Pui-ying ruled that Angela could use the document in a California lawsuit in which she is defending a US$30 million claim by a company her father formerly owned. Angela claims that company is now under Vivien's control.

Angela could also use the document in her lawsuit against Vivien for contempt of court for failing to disclose it under a court order, the judge ruled.

Before his death, Chen was ranked 464th on the list of world billionaires, and 15th among the 39 billionaires from Hong Kong, with net assets estimated at US$2.6 billion.

In April 2011, Yang and Chen reached an agreement to divorce after Yang initiated proceedings in 2009.