Katrin Radmacher, one of Germany’s richest women, is contesting a high court ruling that awarded him £5.6million.
Before they wed 11 years ago Nicolas Granatino, 37, signed a pre-nuptial agreement pledging he would never touch his wife’s wealth if they split up.
But when the couple’s eight-year marriage did finally fail, he changed his mind.
Though Britain’s high court awarded him the one-off compensation payment last year, Ms Radmacher, 42, will try to overturn this next week at London’s Court of Appeal.
If she is successful, divorce lawers believe the case will pave the way for pre-nuptial contracts to become legally binding in Britain, as they are in Europe and in America.
The glamorous couple’s marriage began to crumble six years ago when he quit his well- paid City job to study biotechnology at Oxford University.
They separated three years ago, by which time he was a researcher on £30,000-a-year.
Mrs Radmacher says that if her estranged husband “wishes to be an academic he must live as such”, not as a millionaire.
When the couple met, at Tramp nightclub in London, he earned £320,000 a year as a merchant banker and she ran her a smart boutique in Kensington.
The case is being heard in the English courts because they wed in the capital and also filed for divorce in Britain.
The couple, who have two daughters, were both unavailable for comment yesterday.
Mr Granatino was not at his his £2million flat in Chelsea, and his wife was in Dusseldorf.
At last July’s high court hearing, Mrs Justice Baron ruled it would be “unfair” to hold Mr Granatino to the pre-nuptial. He had not taken independent legal advice before signing and Mrs Radmacher had not disclosed her full worth.
At the appeal court he will be represented by Fiona Shackleton, who acted for Sir Paul McCartney in his acrimonious divorce from Heather Mills.
Julian Lipson, head of family law at Withers, said the heiress was unlikely to succeed. He said: “The English courts pride themselves on protecting the financially weaker party.
“It will override the argument that the weaker party knew what they were signing and should be held to the bargain.”