"Our case is that there must be an account of all the profits, because the assets from which the profits are derived were originally held on trust for us," he said. John Hancock says he is trying to stay true to his grandfather Lang Hancock's wishes. Credit:Philip Gostelow Mrs Rinehart's two elder children, John Hancock and Bianca Rinehart, recently launched new Federal Court proceedings designed to dispute the ownership of assets and shares in their mother's multibillion-dollar empire. They allege that the iron ore rights to significant Pilbara assets – including the revenue-generating Rio Tinto joint venture at Hope Downs and the ­semi-constructed Roy Hill project – were left to a trust for Mrs Rinehart's four children – John, Bianca, Hope and Ginia – by their grandfather, the mining entrepreneur Lang Hancock. Assets 'moved to Hancock Prospecting'

They say that shortly after Lang's death in 1992, Mrs Rinehart man­oeuvred the exploration assets out of the hands of her four young children and into the company she majority owns, Hancock Prospecting. The two elder children also allege that the four children have a right to 49 per cent of Hancock Prospecting, not 23.45 per cent, as it now stands. If the litigation is successful, Mrs Rinehart's wealth, last valued by BRW at $20.01 billion, would be dramatically eroded, as profits from several key assets would flow to the four children. Mrs Rinehart is defending the ­allegations in court. Mrs Rinehart's youngest child, Ginia, has traditionally sided with her mother, however, all four children would share in any legal victory, given they were equal beneficiaries of the ­children's trust.

Representatives of the mining ­magnate have warned that publicity around family litigation posed a risk of commercial harm to the family's mining projects. John Sheahan, QC, for Hancock Prospecting, told the court last month that the case had been brought for the "predominant purpose of harming" the Rinehart family by "extracting ­publicity for the dispute". Temporary suppression order lifted The judge disagreed. A temporary suppression order was eventually lifted and the details of the case are now public. Mr Hancock said if his mother had not breached their trust but had developed the mines in the in­terests of the trusts, as was provided for by their grandfather, then they would be the first to agree that she would have deserved a "good salary" for her stewardship.

"It is not the management of the ­specific projects that we are seeking to have redressed, but the misman­agement of the trusts and our interests," Mr Hancock said. The NSW Federal Court proceedings complement separate litigation in the NSW Supreme Court, which has been running for more than three years. In that court action, Mrs Rinehart's actions as a trustee of assets left to the four Lang Hancock grandchildren have come under question. She has since relinquished her pos­ition as trustee and the court has been charged with appointing a new one. Mrs Rinehart's spokesperson said on Tuesday it was not appropriate to comment on cases before the courts.