Many in the legal profession last week welcomed the Law Commission's proposals to make pre-marital financial agreements, known as prenups, legally enforceable in England and Wales. After all, in places such as South Africa they have been commonplace for decades, and the reform simply brings us more into line with our European neighbours. Law commissioner Professor Elisabeth Cooke declared that prenups, if properly drafted and agreed before a marriage, will "make the financial outcome of separation more predictable". In any case, the courts already recognise prenups following a 2010 legal case, and these proposals would simply make them officially binding.

Yet the very next day, outside a divorce court following a bitter legal battle, wealthy heiress Victoria Luckwell (pictured) was probably thinking quite the opposite. Before marrying in 2005 her husband signed a prenup, and during the course of the marriage he signed further legal agreements to ensure there would be no claim against family assets. Despite the prenup, the judge said the estranged husband, Frankie Limata, was entitled to £1.2m to buy a home and pay off his debts. Speaking after the judgment, Luckwell said her ex had "contributed nothing to my marriage in terms of capital" and described the divorce laws as "a gold digger's charter".

The judge was able to override the prenup because he has to consider the financial needs of each partner – and in this case decided it would be unfair for Mr Limata to be left virtually penniless. Mr Limata had, after all, become accustomed to living in the couple's £6.7m London home just doors down from the Blairs. More importantly, the couple had children – and when they visit him, they should be entitled to somewhere appropriate to stay. Even after the children have grown up, Mr Limata will be entitled to keep around half the value of the house.

The Family Law Courts, as James Ferguson of law firm Boodle Hatfield tells me, must have regard to the standard of living enjoyed by a couple before the breakdown of the marriage. If that involved a high-quality home in a good district, the courts can't just ignore that.

The case was unusual insofar as the wealthier partner was female. But to many (usually men) who feel that divorce awards are often grossly unbalanced, it suggests that prenups are pointless. The most recommended comment on the Guardian's story on the Law Commission report read: "A totally useless proposal. As long as judges reserve the right to interfere, the certainty of a prenup is a completely meaningless concept in English law."

It's hard not to agree. Emily Brand, a partner at Winckworth Sherwood, welcomes prenups for giving more predictability to divorce, but acknowledges that calculating financial needs is a knotty problem – and one the Law Commission has for the time being ducked. Canada uses a formula that some suggest should be imported into the UK. Even so, the courts are unlikely to allow a wealthy person to drop their spouse and rely on a contract that says he or she can be booted out with only the money or assets brought in. The Luckwell case suggests that at the very least the poorer party can be expected to be housed to some degree of comfort, even after children have departed.

In Germany, it's very different. There, the Dusseldorfer Tabelle precisely set out child maintenance payments, and apart from that the courts can enforce a strict interpretation of premarital agreements which may result in one partner being left with almost nothing. Harsh, maybe, but unfair? If the agreement was entered into without duress, where each had separate legal advice, why should such a contract not be adhered to?

In the meantime, as Ferguson points out, if protecting your assets are what you are chiefly concerned about, then in reality the only way to do so is to not get married.