A London divorce court judge has been asked to decide whether or not a wealthy Russian businessman and his estranged wife are already divorced.
The man, who is involved in the Russian oil business and has a home in Switzerland, says they divorced in Russia more than a decade ago.
His estranged wife, who lives in England, says she knew nothing about a divorce until she came across documents in a safe.
She says he obtained a "fraudulent" divorce in Russia. She says she should be allowed to launch divorce proceedings in England and that an English divorce court judge should make decisions about the division of money.
Mrs Justice Parker analysed the dispute at a Valentine's Day hearing in the Family Division of the High Court in London.
She said she had to decide whether or not the couple had been divorced in Moscow in November 2006.
The judge, who says "vast amounts" are at stake, is expected to make a decision later in the year following a further hearing.
She has ruled that the family cannot be identified.
"This is a very hard fought case with vast amounts at stake on both sides," said Mrs Justice Parker on Wednesday.
"The husband is adamant ... that they were agreeable to divorce - and the required practice of the Russian court was complied with."
She added: "It is the wife's case that she never knew there was a divorce until she discovered documents in a safe kept by the husband in a property in Russia."
Detail of the family's lifestyle emerged a few months ago after another London-based High Court judge analysed a separate row over the custody of their two teenage sons.
Mr Justice Peter Jackson said, in a ruling on the dispute over the children, that the family had "every conceivable material advantage" but money had not bought happiness.
He said they had run up close to £1 million in lawyers' bills on the fight over the children alone.
The judge concluded that the two boys, who had been living with their mother in England, should move to Switzerland to live with their father.
Mr Justice Jackson said the man fathered a son by a woman who had worked for his wife.
The man had told his sons about the baby but not his estranged wife.
She had learned about the little boy's birth from her lawyers.
Mr Justice Jackson described the way the man had behaved as "shabby".
He said the family, who also have Cypriot citizenship, had forgotten how to do "simple things".
"In a case of this kind, where a family has every conceivable material advantage, it is easy to forget the old truth that money cannot buy you happiness," he said.
"It certainly has not done for this family. Instead, the pursuit and accumulation of wealth ... has created conditions that have left everyone spoilt for choice and thoroughly miserable."
The judge said the children had grown used to the "usual trappings" of an opulent lifestyle - lavish homes, privileged schools, incessant international travel and being constantly surrounded by staff of one kind or another.