Gina Rinehart's eldest daughter and former heir to the Hancock empire, Bianca Rinehart, married in secret seven months ago without telling her mother.
Mrs Rinehart, who is locked in a bitter dispute with Bianca and her brother John Hancock, was not invited to the wedding and had no idea her daughter was married until yesterday, when her lawyers were shown the wedding certificate.
The "secret wedding" has embarrassed the mining magnate and laid bare the depth of animosity in Australia's most famous family feud.
Bianca Rinehart and her long-term partner Sasha Serebryakov were surrounded only by a small group of friends when they were married in a private ceremony in Hawaii.
The wedding was in April, midway through the Hancock family's bitter court battle and shortly after Mrs Rinehart made a public show of family unity when she cruised the Swan River on a $7.5 million superyacht with her two other daughters Ginia Rinehart and Hope Welker.
_The West Australian _understands that none of the three was invited to the wedding or knew about it until yesterday. Bianca and Mr Serebryakov, a 32-year-old Russian-born business development manager in Rio Tinto's uranium division, have been living together for six years and have a three-year-old son. Yesterday, their Hawaiian wedding celebrant described the pair as an "amazing couple".
About 20 guests attended the ceremony, where they drank mai tais cocktails and were entertained by a hula dancer.
Bianca and her new husband danced to Bob Dylan's You Belong to Me. She later described the wedding as "everything I had hoped for and more".
"My friends who were present have told me they have never seen me so happy in my entire life," she wrote in a letter of thanks to the celebrant.
News of the wedding blindsided the Rinehart camp yesterday, who had fronted the NSW Supreme Court planning to challenge an eleventh-hour bid to put forward Mr Serebryakov as a potential head of the multibillion-dollar family trust on the grounds that the pair weren't married.
A photocopy of the Hawaiian wedding certificate, provided by Bianca's lawyer Christopher Withers was passed in court to shocked lawyers for Mrs Rinehart and Ginia.
"This secret marriage that took place was a pretty good reason for objecting (to Mr Serebryakov's appointment)," Ginia's lawyer Richard McHugh said. The revelation came as both sides admitted they were no closer to ending the impasse over who would head the family trust, which owns almost a quarter of family company Hancock Prospecting.
Two months ago, Mrs Rinehart agreed to step down as trustee, just days before a trial into her fitness to hold the role and after months of calls from her estranged children Bianca and Mr Hancock to resign.
A hearing into the trust's future ended last month, with Justice Paul Brereton asking both sides to agree on a suitable replacement. Yesterday, with no sign of progress on agreement, he suggested Hancock Prospecting forfeit its stake in its Hope Downs joint venture with Rio Tinto as a means of resolving the dispute.
Hancock Prospecting has a lucrative joint venture agreement with Rio to develop the Hope Downs mine in the Pilbara.
Under the deal, Hancock Prospecting shares have to be held by a lineal descendant of Mrs Rinehart, or a spouse of one of her children, otherwise a clause is triggered that allows Rio to buy Hancock Prospecting out of the venture.
Justice Brereton said if Hancock's share was bought by Rio, there would be money available to the company to pay to the four children, who were its beneficiaries, in order to satisfy any capital gains liability.