Why the exes of the wealthy want to get divorced in London

January is famously the month in which more people file for divorce than any other. And if your marriage is at an end, you're a member of the international jet set and earn less than your partner, London seems to be the best place to secure a generous settlement.

The most recent divorce case to hit headlines is that of former Miss Malaysia Pauline Chai, whose Malaysian tycoon husband Khoo Kay Peng is chairman of U.K. retailer Laura Ashley. Chai is asking for £500 million, around half her husband's fortune, in London's courts, but Peng wants the case, which is ongoing, to be held in Malaysia.

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There are plenty of reasons why the less-wealthy party would prefer to be divorced in London, and this has led to a buoyant market for family law firms in the capital.

"London's place in the world has meant a lot more work for family lawyers than even 15 years ago, across the income spectrum," William Longrigg, partner at Charles Russell and president-elect of the International Academy of Matrimonial Lawyers, told CNBC.

(Read more: How to avoid divorce settlement blunders)

The U.K. courts are more likely to divide assets equally, even if one spouse has brought more financially to the marriage and much harsher on spouses who try to hide their assets. In one famous case, the McFarlane divorce, the wife was awarded £250,000 for life after giving up a career as a solicitor to raise the couple's children. And Heather Mills was awarded secured £24.3 million when she split from former Beatle Sir Paul McCartney.

(Read more: The most divorced celebrities)

The most important factor in London's popularity is the amount of freedom given to its judges to be flexible with maintenance awards, according to a recent study by family law firm Withers.

"The judge can take a lot of factors into account and vary them, whereas in other jurisdictions there's more of a formula for what you can award," Suzanne Kingston, partner at Withers, told CNBC.

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In jurisdictions like France and Germany, as well as some of the U.S. states, there is less chance of being awarded long-term maintenance and judges have less leeway in granting awards.

Even when the initial divorce occurs outside London, assets can still be divided in a U.K. court. One of the most high-profile examples of this is the break-up of Russian oil tycoon Alexei Golubovich and his wife Olga Mirimskaya, who divorced in Russia and are currently disputing ownership of a £6.4 million West London property.

London itself has become more attractive to the wealthy – whether they are French fleeing 75 percent tax or Russians enjoying a more cosmopolitan city than Moscow. This has driven up the cost of prime real estate in the city, but also the number of wealthy people resident in London or with a London home from which to launch proceedings.

While behavior during a marriage is not usually a factor in financial settlements in London, British judges do take a dim view of failure to disclose assets. Scot Young, who has been declared bankrupt, found this out to his cost this year, when he went to prison for six months for contempt of court over attempts to hide his fortune. The Young case was notorious for the length of time and money taken to pursue the husband's assets, and concluded in November with a £20 million ($33 million) award to wife Michelle Young – although she claims that her husband is worth much more than the £45 million the judge ruled.

(Read more: Wife calls $33 million divorce payout 'disgraceful')

"There is a saying that "non-disclosers lose" in these cases," Longrigg said.

Still, in cases where assets are believed to be hidden, the poorer party often has to concede that they may never trace all of them, and accept a settlement.

"Quite often, clients are pragmatic about what they can achieve," Longrigg said.

"Pursuing hidden assets is incredibly expensive and, very often, not worth it."