Family/Matrimonial Finance: Ultra High Net Worth: A London (Firms) Overview

During the course of 2025 there were several cases with far-reaching consequences for high net worth families.

The latest decision in the long-running litigation of Potanina v Potanin was delivered by the Court of Appeal in September 2025 concerning applications brought in England and Wales under Part III of the Matrimonial and Family Proceedings Act 1984 for financial relief after a foreign divorce. The parties to this case divorced in Russia in 2014. The wife subsequently moved to England and in 2018 applied for permission on a “without notice” basis to make a Part III claim for financial relief (it being her case that she received less than 1% of the marital wealth in the Russian divorce – USD41.5 million – as a result of the husband’s corporate and trust interests worth billions being excluded from the division of assets). The court initially granted the wife leave to make this application, but there then followed years of litigation up to the Supreme Court in 2024. Although the Supreme Court upheld one aspect of an appeal brought by the husband, clarifying that the court does not require a “compelling reason” or “knock out blow” to set aside a grant of permission for an application, the court also found that the wife’s case should not be dismissed as the husband sought and should instead be remitted to the Court of Appeal to reconsider whether leave should be granted for her to proceed with her application. The Court of Appeal held that the wife had a “real and meaningful connection” to this jurisdiction and a “substantial ground” for an application under Part III when the application was made. Accordingly, the wife’s substantive claim has been remitted to the High Court for determination, and the case continues.

In the case of Standish v Standish, the Supreme Court delivered a highly anticipated judgment on the extent to which non-matrimonial assets can become matrimonial and therefore subject to sharing on divorce (otherwise known as “matrimonialisation”). In 2017, Mr Standish transferred GBP77.8 million of pre-marital assets to Mrs Standish as part of an inheritance tax mitigation strategy, intending for the funds to be settled in trusts for their children. The trusts were never established, however, and the wife retained the assets in her name. The first-instance judge considered those assets matrimonialised and therefore to be shared with the wife, albeit unequally. The Court of Appeal disagreed, saying that the source of an asset, not who holds it, is critical and that while the concept of matrimonialisation still applied, it should be applied narrowly. Mrs Standish’s overall award was reduced from GBP45 million to GBP25 million as a result. The Supreme Court upheld the Court of Appeal’s decision. They stated definitively that the sharing principle applied only to matrimonial property and that the concept of matrimonialisation should not be applied narrowly. The court should, they said, look at whether an asset is treated by the parties over time as a shared asset. The Supreme Court also held that assets transferred between spouses to save tax should not be treated as being shared between them without compelling evidence to the contrary.

ST v AR (heard before the Supreme Court’s judgment in Standish) was an example of a big-money case (nearly GBP150 million) where the assets were inherited and held to have had remained non-matrimonial, such that the question for the court was how generously the wife’s needs would be assessed. The wife received just under GBP14 million. In GR v AR, another high net worth case heard before the Supreme Court’s judgment in Standish, the wife’s pre-marital wealth was taken into consideration by the judge to arrive at a 60.9%/39.1% split in her favour. This case distinguished the family home as different from other assets in the marriage and as one which will typically be shared regardless of whose name it is in.

Another issue at the forefront of some big-money cases this year has been the court’s treatment of pre- and post-nuptial agreements. When significant wealth is built up during a marriage, the temptation to dispute the terms of a nuptial agreement can be hard to resist. In PN v SA, the parties entered into a post-nuptial agreement in 2021, which provided for the equal division of assets, followed by a subsequent post-nuptial agreement in 2023, which was signed post-separation. The court had to grapple with whether the 2023 agreement should override the earlier agreement. The assets at the final hearing were valued around GBP500 million. The wife’s position was that the 2021 agreement should be upheld on the basis it was freely entered into and provided for an equal division, while the 2023 agreement was signed under undue pressure and was less fair. The husband’s position was that the parties should be bound by the 2023 agreement. The court found that the 2021 agreement was valid, while the 2023 agreement was not, as the wife did not receive full legal advice when signing and faced undue emotional and financial pressure from the husband. The wife received GBP230 million, the third largest reported award in English legal history.

The case of BI v EN centred around whether a French marriage contract signed seven days before the parties’ wedding adopting the separation de biens marital regime (ie, with each spouse retaining ownership of their own assets and debts) should be upheld. The wife claimed she did not understand its implications. The husband had amassed estimated wealth of around GBP100 million. The wife argued that this was matrimonial and should be shared, while the husband relied on the agreement. The court gave the agreement decisive weight, and so the wife did not share in the husband’s assets. Instead, she received a needs-based settlement, which was generously assessed due to the length of the marriage and standard of living, amounting to GBP23 million.

In the case of Helliwell v Entwistle, the Court of Appeal overturned the High Court’s decision to uphold a pre-nuptial agreement where the wife had failed to disclose around 73% of her assets (roughly GBP48 million) when the agreement was signed. The court found that her omission amounted to fraudulent non-disclosure. The agreement was considered to be invalid and the wife was ordered to pay the husband’s costs. This case emphasises the onus on both parties to provide full and frank disclosure and the importance of obtaining legal advice.

In BR v BR, the husband founded a technology business worth circa GBP200 million during the marriage. Both parties accepted it was a sharing case. The wife sought to continue to hold shares in the company alongside the husband, and the husband sought to buy out the wife’s interest. The court noted that parties continuing to share assets should be avoided where possible. In this case, the court found that it would be unworkable: it risked conflict not only between the parties but also between the wife and other shareholders and management in the business. The husband was ordered to buy out the wife’s share, allowing for a clean break. The husband received 55% of the overall assets, and the wife 45%, taking into account that the husband retained risky and uncertain business assets in a volatile sector.

The case of KV v KV involved a jurisdictional dispute with assets worth many billions of pounds. In KV v KV (No 1), as well as ordering the husband to pay the legal costs of the wife, totalling nearly GBP750,000, the court ordered that the husband should pay interim expenses plus maintenance to the wife of almost GBP4 million per annum. In KV v KV (No 2), the court determined that the wife was habitually resident in England and that the English court was the appropriate forum.

The Schedule I case of W v X concerned unmarried parents, which meant that the mother was not entitled to a share in the father’s wealth, but instead she could apply for housing and income provision for herself and their child. In this case the father’s total resources amounted to roughly GBP67 million and his income was put at GBP3.275 million. By contrast, the mother’s resources were found to be GBP991,000, with no income. The standard of living enjoyed by the child during the parties’ relationship was found to be a “highly material factor”. The father was ordered to meet rental payments of GBP172,800 per annum for the child to remain living in the family home with the mother and to pay maintenance payments of GBP225,000 per annum (CPI linked) plus school fees and a lump sum to cover her debts and legal costs.

Finally, simply obtaining an award may not be enough if the spouse refuses to pay. In enforcement proceedings in the very long-running case of Collardeau v Fuchs, the court found that a purported lease over the husband’s property in the Cotswolds was a sham designed to defeat the wife’s claim for financial relief (she had been awarded a circa GBP19 million lump sum). The lease was set aside.