Two millionaire half sisters are facing off in an "obsessive" court row over ownership of a £2.7m New Forest mansion.Lindsay Bisiker, 50, and older sibling Judith Bisiker, 63, - who she regarded as her "surrogate mum" as a child - are fighting in London’s High Court over “Moonhills”, a six-bed house in four acres with stables and a tennis court, bought by their ex-Royal Marine turned oil tycoon dad Jim Bisiker, in 1984.Much of the Bisiker family are now based in Canada, but Lindsay says the house on the edge of Beaulieu became her “home base” in the UK while attending boarding school and during holidays.Despite now owning her own £2.3m farm in Devon, she says it remained a powerful “grounding force” for her.But it caused a war to start with her previously idolised half-sister after Judith declared the mansion belonged to her alone and that she wanted to put it up for sale.Although paid for by dad Jim, now 95, the property was put in Judith’s sole name and she says she has a right to sell it if she wants.Moonhills mansion in The New Forest (Supplied by Champion News)The clash between the half sisters turned nasty, with Judith accusing Lindsay of having an "obsession" with Moonhills, and Lindsay claiming her older sibling had her "evicted" by changing the locks while she was staying there with her dogs in April 2023.Lindsay is now suing, claiming the property - despite being Judith's on paper - was always intended to be "held on trust" and shared with the whole family.She wants it to be sold to her at a discount rate so that it can stay within the family and wants the right to move in in the meantime.Judith for her part wants to put the house on the open market, insisting she was justified in having the locks changed and Lindsay excluded to stop her trying to "frustrate the sale" of the property.Moonhills, a six-bed five-reception house, with four acres of grounds including a tennis court, double garage and stabling for two horses, is set in the idyllic heart of the New Forest and has been in the Bisiker family for over 40 years.With her parents often away in Canada, Judith had helped “raise” her at Moonhills, a tearful Lindsay told the High Court, and her older sibling - 13 years her senior - acted as her “surrogate mum” as she looked after her at the sprawling country spread where the pair could also indulge their shared love for horses.Judith Bisiker outside court (Champion News)Both sisters had developed the same passion for equestrian eventing, with Judith once an Olympic hopeful for the Canadian three-day event team and who now runs a stables and riding school in Ontario, whilst Lindsay owns eventing horses.The bitter dispute which has now rocked the family was sparked by the two sisters’ competing plans for the future of Moonhills and their conflicting understanding about its ownership, with Judith keen to sell up at a market price and Lindsay desperate to hang onto her childhood home.Lawyers for Lindsay say Moonhills was acquired by Jim Bisiker with the clear intention of Judith holding it “on trust” for the entire Bisiker family to occupy, comprising the two warring sisters, their parents, Jim and Brenda, and three other siblings, Brian, Heather and Malcolm Bisiker.James Sandham, for Lindsay, in arguments presented at a hearing earlier this year said dad Jim had backed Lindsay's version of events in written documents dating from 2016 to 2023 and in a witness statement."Moonhills has always operated as a family base for the children to come and go as they please," said the barrister. "The children have not been required to pay any form of rent and Moonhills has generally been maintained by money provided by Jim."The court should proceed on the basis that by evicting and/or excluding Lindsay from Moonhills and attempting to sell it, Judith has...acted in breach of trust and contrary to Jim’s wishes."Jim did not want the property sold, his preference was for one of his children to purchase it such that it remains within the family."Consistent with the way it has always been used, Jim made clear that Moonhills should remain available for the use and access by the family, including for Lindsay’s ongoing occupation in it as her home."The circumstances in which Judith evicted Lindsay on 29 April 2023 are particularly troubling...there was apparently no consideration of all the beneficiaries’ views."Judith’s denial of Lindsay’s claim to have been in occupation at the time of the eviction is ludicrous...Lindsay’s dogs were inside at the window and Lindsay was permitted in to collect her personal items."The terms of the trust are clear, having been agreed and understood by the family."Jim Bisiker (Supplied by Champion News)He said Jim's witness statement of May 2023 confirmed that the house is held by Judith on trust to be used as a family home and specifically for Lindsay to live in until she can purchase it herself.Arguing that Lindsay should now get a discount rate to buy the house, he added: "It may be that a 'fair' price would be less than a price a third-party would pay if that would ensure that Moonhills remains in the family."But James Saunders - barrister for Judith - argued that she “holds both legal and beneficial title, unburdened by any trust obligation”.He told the judge, Master Matthew Marsh: "Jim was born in 1929, lived in the UK for a period and emigrated to Canada in the 1950s."In 1981, Judith, aged 21, moved to the UK after completing her studies in Canada. Initially Judith rented a small property, but her father felt she needed a more permanent home and a property search began."Judith purchased Moonhills in 1984 and the property was registered in her sole name. Jim paid the purchase price."Judith’s case is that she has always been and remains the sole owner of Moonhills. Jim purchased the property in Judith’s name intending her to be the owner in law and in equity...principally in order that Moonhills should fall outside his estate for inheritance tax purposes."Lindsay Bisiker outside court (Champion News Service Ltd)Detailing the row between the half sisters, he continued: "Discussions around putting Moonhills on the market for sale began in around 2021. Lindsay expressed an interest in purchasing which intensified over the following years into an obsession, with Lindsay writing in September 2022 that the house 'isn't going to be sold to anyone but me'."Relations dipped lower the following year after Lindsay took exception to some of the market valuations secured by Judith, said the barrister, and tensions then came to a head when Lindsay allegedly “changed the locks” at Moonhills in January 2023, prompting Judith’s lawyers to send out a letter ordering her to “quit” the house.In response, Lindsay threatened there would be a “huge battle with violence” if Heather and her older half-brother, Brian, visited Moonhills, claimed Mr Saunders, but in April 2023 Judith sent in a security firm to “secure” the property and change the locks to bar Lindsay from the house.Lindsay now claims she was unlawfully evicted from Moonhills by Judith and seeks compensation for the effect on her of being excluded from her childhood home in April 2023, also claiming her older sister failed to consult properly with other family members before taking such a drastic step."Judith will say that Lindsay has used and stayed at Moonhills over the years, as have the wider family, but Moonhills has not been Lindsay’s home," said the barrister."Judith made clear that Jim and Brenda in particular, as well as other members of the family in due course, could stay at Moonhills whenever they wanted to. "Jim asked Judith to allow members of the family to share the use of Moonhills for so long as that remained practical, and she confirmed that she would honour that request."The informal wish of Jim’s for family use of the property never amounted to conferring any beneficial ownership shares on anyone."The barrister also dismissed Jim's backing of Lindsay, saying an assessment in 2023 had shown that he lacked mental capacity."Any suggestion that Jim’s incapacitous statements from the past four years are of relevance...would be mistaken," he said.From the witness box, Lindsay said her dad had deliberately planned for Judith’s name to be on the title deeds as owner for tax reasons, but that he was clear that Moonhills should be a family asset.“I was always reassured that it was held on trust for the whole family,” she told the court, adding: “Judith helped with running the house but dad never lost control of that house financially.“I lived there and it was my home and Judith raised me there. I was led to believe that it was the Bisiker family home and my father actioned it in that way.”When Canadian-born Lindsay went to boarding school in England in 1991, Moonhills became a “safe space” for her, she told the court, spending school breaks and other holidays there with Judith also generally in residence.“Sometimes my parents would come over and we would spend Christmas there, I’d spend half terms there. I had all my stuff there, and had my horse there.“Judith was my surrogate mum,” she told the court, also adding: “my parents would spend time there as well, and we would create memories.”Judith, however, says Moonhills was always intended to be hers to do as she wishes, although accepting a “moral obligation” to follow her dad’s wish that other family members should be able to use the house where possible.And although she relocated to Canada in 2011, her barrister pointed out that Judith had made Moonhills her home from the age of 21, living there for a decade until 1995.Lindsay’s parents, Jim and Brenda Bisiker, have been joined as parties to the court dispute, as have her other siblings, Brian, Heather and Malcolm.The trial is continuing.