Vladimir Potanin, co-owner of Norilsk Nickel, attends an agreement signing ceremony with the Krasnoyarsk region's government, in Moscow, Russia December 12, 2017.
Vladimir Potanin, co-owner of Norilsk Nickel, attends an agreement signing ceremony with the Krasnoyarsk region's government, in Moscow, Russia December 12, 2017. Image Credit: Reuters

A British legal dispute between Russia's richest man, Vladimir Potanin, and his ex-wife over a multi billion dollar share of his mining assets is set to continue in one of the world's largest divorces.

In a split decision on Wednesday, the UK's Supreme Court ruled in favor of the sanctioned billionaire in a judgment that may bring tougher scrutiny to claimants who previously divorced overseas. However, the judges declared further court hearings are required.

Potanin had attempted to fully knock out the claim brought by his former partner, Natalia Potanina, who is seeking permission to bring a suit worth at one point as much as $9 billion.

London's divorce courts have been a popular destination for high-value legal fights, with judges typically prepared to order a more equal share of a couple's assets. In the UK, the largest publicly known payout in a divorce is currently Pound450 million ($571 million) to the wife of billionaire Farkhad Akhmedov "- though the two settled with a payment of less than one-third of that amount.

In the 3-2 decision, the judges decided that there had been procedural unfairness in the way that an appeal court had considered whether to permit the claim to continue.

"The court is required to decide afresh, after hearing argument from both sides, whether the order should be made or not," Judge George Leggatt said in the ruling.

Both sides welcomed the ruling. Potanin's lawyers said English courts would now need to bring tougher scrutiny before allowing cases to proceed following an overseas divorce.

"Divorce tourists will now have their claims subject to fair and robust scrutiny before being granted leave in this jurisdiction. It is long overdue," said Fiona Shackleton, Potanin's lawyer at Payne Hicks Beach.

The senior judges said they looked forward to considering whether English courts should allow claims for financial assistance from individuals "whose connections with this country are slight." But they said that must "await a case in which the issues arise from the decision under appeal."

"The Court of Appeal will now focus on the merits of her case rather than on procedure," said Frances Hughes, Potanina's lawyer at Hughes Fowler Carruthers.

Potanin has amassed a fortune of around $31.8 billion largely from MMC Norilsk Nickel PJSC, the world's largest producer of high-grade nickel, according to the Bloomberg Billionaires Index.

Lower court judges previously said that Potanina received a "paltry award" in prior Russian divorce proceedings, given the billionaire's wealth and the length of their 31- year marriage.

The case has swung back and forth with a lower court ruling accusing Potanina of "divorce tourism" before she then won an appeal. The two lived in Russia throughout their marriage before Potanina bought a home in Westminster in 2014. Potanina is seeking 50% of the value of his stake in Nornickel alongside dividends. That amount would far exceed $5 billion, given that Potanin owns around one-third of the shares in the metal producer.

Potanin has taken advantage of restrictions on foreign ownership of Russian assets since the Kremlin invaded Ukraine by branching out into finance and buying stakes in banks as foreign owners pulled out. Potanin was sanctioned by the UK after buying a stake in Rosbank PJSC and later placed on the US blacklist. Before that, Potanin had largely avoided western sanctions that hit other members of the Russian elite.

Nornickel has avoided Western sanctions, but fallout from the invasion of Ukraine has disrupted its logistics and shipping operations.