(Bloomberg) -- Vladimir Potanin, Russia’s richest man, faces one of the largest divorce fights the U.K. courts have ever seen after London appeal judges cleared the way for his former wife to renew her claim against him.

The billionaire’s ex-wife Natalia Potanina overturned a lower court ruling which had accused her of “divorce tourism.” The couple divorced in Russia in 2014 and she is seeking a further award of as much as $6 billion, that would dwarf the largest publicly known payout in a U.K. divorce.

The husband is still able to appeal Thursday’s decision to the U.K. Supreme Court.

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. The record award is currently 450 million pounds ($631 million) to the wife of billionaire Farkhad Akhmedov, but he is yet to pay her a penny.

Potanina said she received around $40 million following Russian divorce proceedings while Potanin said she ended up with $84 million -- a sum that by English standards is a “paltry award,” given the billionaire’s wealth and the length of their 31-year-marriage, a judge said in a previous decision. The appeal judges appeared to agree on Thursday.

“No doubt to most people, whether affluent or poor, the sums received by the wife made her a rich woman,” Judge Eleanor King said in the ruling. “Everything is, however, relative. The wife’s settlement represented only a tiny proportion of the vast wealth of this family.”

Potanin, Russia’s richest tycoon with $33.5 billion fortune -- the 37th richest person in the world according to the Bloomberg Billionaires Index -- is considered to be one of the few “oligarchs” who became rich under Russian President Boris Yeltsin. He’s the president of MMC Norlisk Nickel PJSC, the world’s largest producer of high-grade nickel.

A spokesman for Potanin declined to comment and lawyers for Potanina couldn’t immediately be reached.

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