The billionaire's account of her father's last years of alleged dishonesty was concocted to defend a rival mining dynasty's claim for tenements and royalties, said Christopher Withers SC, representing Mrs Rinehart's children.
"The argument that Lang was breaching his duties to (Hancock Prospecting) and that he concealed that fact from Gina and acted dishonestly, those arguments are complete fiction as part of the false narrative," he told the trial on Tuesday, referring to Mr Hancock's business decisions after marrying his housekeeper Rose Porteous in 1985.
Hancock Prospecting's lawyers last week also detailed the spat between Mrs Rinehart and her father as it made its defence case against the company of Lang Hancock's former business partner, Wright Prospecting, which is claiming tenements and royalties linked to the lucrative Hope Downs mining complex.
Noel Hutley SC alleged Lang Hancock attempted to leave considerable wealth to Mrs Porteous, who Mrs Rinehart vehemently disapproved of, amid breaches of his fiduciary duty before realising "the error of his way".
The Supreme Court heard Mr Hancock showed "no regard" for Wright Prospecting's interests, which was contrary to the company's claim that he was acting for the Hanwright partnership.
Mr Withers on Tuesday said Mrs Rinehart's false narrative regarding her father was also the version of events she told her son, John Hancock, in 2003 when he realised his grandfather's plan to leave him and his sisters a 49 per cent share in the family business empire under a 1988 agreement had been undone by his mother, triggering a bitter legal dispute that is raging in another court.
Mr Withers, who is defending John Hancock and Bianca Rinehart against Wright Prospecting and another company's claims, also took Justice Jennifer Smith through the events before Lang Hancock died.
That included detailing two deeds Lang Hancock wrote before he died in which he left his wife "big money" then attempted to undo the pledge after he mended his relationship with his daughter.
Mr Withers also outlined an attempt by Mrs Rinehart in the years before to remove her father as a director of the family's companies and install herself and her then-husband Frank Rinehart in his place.
Mr Withers read a 1989 letter to the court from Lang Hancock to his daughter in which he begs his daughter to stop contacting him amid a feud over his business decisions and marriage to Mrs Porteous that included Mrs Rinehart racially abusing her and attempting to have her deported.
"I would be pleased if you leave me alone to live the rest of my life in peace," Mr Withers said reading from the letter.
"He had been fighting with Gina for years ... On many occasions, he had pleaded with Gina to stop her barrage of criticisms."
The Hope Downs mining complex near Newman is one of Australia's largest and most successful iron ore projects, comprising four open-pit mines.
Mrs Rinehart, the executive chair of Hancock Prospecting, secured the development of the mines after signing a deal in 2005 with Rio Tinto - which has a 50 per cent stake in the project.
Hancock Prospecting last week accused Lang Hancock of breaching his fiduciary duties by diverting tenements without disclosing the moves to Mrs Rinehart but Mr Withers has disputed this.
The company also maintains it undertook all the work, bore the financial risk involved in the development at Hope Downs and is the legitimate owner of the assets.
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