Mr Hamilton bequeathed £500,000 to his widow, Laura, and the remaining £4 million of his UK wealth was split equally between his children, Alan and Carolyn Hamilton.
The siblings were also bequeathed £3.2 million in assets held by a foreign foundation set up by their father - which is now the focus of the bitter conflict.
Alan, 69, an accountant, received £1 million from the Rainbow Foundation after his father's death, while barrister Carolyn, 64, got £2.2 million.
He now claims that the funds in the Foundation should be split 50/50 in line with his father’s will.
Carolyn's lawyer described the case as a "deeply unattractive claim" and argued that Alan was effectively accusing his father of being a tax dodger who moved his cash overseas to deceive HMRC.
But Carolyn insisted that her father would never have cheated the taxman.
"My father was heavily affected by his pre-war experiences," she told the court.
"He lost his family, his home, his country and his community. He lost everything.
"He was always concerned that it would happen again.”
The hearing continues.