The Oxford student in pre-nup battle with heiress

This is the Oxford student at the centre of a landmark divorce battle over his wife's £100million fortune.

Nicolas Granatino, 38, who lives in a £7,000 a month flat in Knightsbridge paid for by his ex-wife, was awarded £5.5million despite signing a pre-nuptial contract promising not to make a claim on her inheritance.

Now Mr Granatino has an anxious wait to discover if his former wife Katrin Radmacher has been successful in getting his payout overturned by the Court of Appeal. She wants the pre-nuptial contract signed by the couple in Germany before they married to be recognised as valid under English law.

Far from being an impoverished PhD student, Mr Granatino is the son of a wealthy French industrialist. His father Antoine, who lives in London for tax reasons, could be worth as much as £30million although his son insists his wealth is closer to £6million.

Antoine, a former vice-president of computer giant IBM, lives in a flat in Kensington next to Hyde Park as well as retaining a villa in Antibes.

But because English law does not take into account any future inheritance, the High Court judge who awarded Mr Granatino his £5.5million payout was unable to speculate on what he might be worth when his father dies.

Ms Radmacher, 39, was already worth millions, having been given six per cent of her father's paper-making empire.

The couple, who met in Tramps nightclub, married in London in November 1998. Mr Granatino quit his job in 2003 as a banker with JP Morgan, where he earned more than £325,000 a year at the peak of his career, to study for a doctorate in biotechnology at Oxford. Court papers reveal that he continued to enjoy the trappings of wealth. Mrs Justice Baron, who presided over the High Court divorce case, concluded that Mr Granatino "likes to feel rich... eating in the best restaurants, driving an upmarket car and spending at will".

In a little over a year, according to court papers, he spent more than £115,000 on holidays alone. In her High Court ruling handed down last year, Mrs Justice Baron added that Ms Radmacher was "far nicer, being more engaging and open" than her husband.

She described Mr Granatino as "superficially very charming", adding: "The husband likes the good life with its attendant luxuries." But she dismissed Ms Radmacher's claim that her husband had deliberately delayed his PhD to maximise his divorce settlement. Following the High Court ruling, Ms Radmacher, who now lives in Germany with the couple's two young children, took her case to the Court of Appeal. Senior judges will rule on the validity of the pre-nuptial contract at the end of this month.

Ms Radmacher's legal team is Ayesha Vardag, one of the capital's best known divorce solicitors, and the eminent QC Richard Todd. Mr Granatino has so far run up debts of about £800,000, much of it to assemble Britain's most expensive and feared divorce pairing of Fiona Shackleton and Nicholas Mostyn, QC, who represented Sir Paul McCartney against Heather Mills.