The status of prenuptial contracts in England will be tested in a landmark appeal in London next week when a multimillionaire German heiress seeks to enforce an agreement that would leave her husband with nothing.

Katrin Radmacher, a paper industry heiress worth an estimated £100 million, claims that her estranged husband is seeking to renege on a deal the couple made before they married in London in 1998 in which he agreed not to claim against her if they separated.

The estranged husband, Nicolas Granatino, has hired Fiona Shackleton, London's best known divorce lawyer who advised Sir Paul McCartney is his split with Heather Mills, to act over his claim of a share of her fortune when the case comes before the Court of Appeal.

A High Court judge has already ruled during their divorce proceedings in July that it would be "manifestly unfair" to hold Mr Granatino to the deal, given their respective financial strength, and ordered that Ms Radmacher make a one-off payment of £5.6 million.

Mr Granatino is an impoverished former investment banker but was earning £1.5 million a year.

If Ms Radmacher succeeds in challenging the award, the ruling will mean that pre-nuptial contracts, widely recognised in Europe and obtained there by many foreign couples who subsequently come to London, are legally enforceable in England.

It would also strengthen the enforceability of pre-nuptial contracts generally in the UK courts.

One divorce lawyer said: "For him to get nothing would seem a bit harsh, given that she is worth some £100 million."

Mr Granatino, a French national who worked for JP Morgan, gave up his banking career six years ago to pursue a doctorate in biotechnology at Oxford.

The couple's marriage broke down shortly afterwards, culminating in formal separation in 2006, eight years after they were wedded.

He says that he can now expect to earn just £30,000 a year as an academic researcher and has accumulated debts of several hundred thousand pounds.

Under their pre-nuptial agreement, executed in German law four months before their marriage, both parties agreed not to make a financial claim against the other if they split up.

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