Fund manager Randy Work has asked judges to weigh the value of his "genius" as he tried to get a bigger slice of his family's $US225 million ($297 million) fortune than his ex-wife. He lost.

The former Lone Star Funds executive failed to convince a three-judge panel at his divorce appeal in London this week that his "special contribution" during their marriage meant he was entitled to a bigger share than the typical British practice of awarding a 50-50 division of marital assets.

Work and Mandy Gray, both American, were married for 20 years when they split. A lower-court judge said in 2015 that the multimillion-dollar estate should be equally split because while Work may have worked hard, the fortune was the result of "being in the right place at the right time, or benefiting from a period of boom," not his professional brilliance.

The appeal judges agreed, saying the use "of the word genius is unhelpful," and that Work "failed to demonstrate that" the previous judge's "decision was wrong."

Mozart, Einstein

"The word 'genius' tends to be over-used and is properly reserved for Leonardo Da Vinci, Mozart, Einstein, and others like them," Judge Edward Holman said in the 2015 decision, rejecting the special contribution argument.

British appeal judges have only ruled on the issue of special contribution a handful of times in the last 15 years as they have tried to draw a line between success of a "wholly exceptional nature" and people who've become very wealthy through ordinary means.

Work, who had asked for 61 per cent of the assets, applied "groundbreaking methodologies" in the Japanese distressed debt market while running the fund's office there, generating huge returns, according to the ruling.

He was "undoubtedly, very successful" but he didn't create Lone Star, the judges said, citing the 2015 ruling.

Lawyers for Work and Gray didn't immediately respond to emails requesting comment.

London courts have gained a reputation as being a more sympathetic place to play out high-stakes divorces, as generally speaking judges order a 50-50 split of assets, giving equal weight to the work of a wealth creator and a home maker. However, when they do rule in favour of it the numbers involved can be eye catching.

Advertising agency WPP boss Martin Sorrell relied on it in his 2005 divorce, in which a judge ruled his contribution was exceptional and awarded his ex-wife 40 per cent of their £75 million of assets.

'Extraordinary talent'

The next year a judge gave the ex-wife of Axis Capital Holdings's then CEO John Charman 36.5 per cent of their £131 million marital estate on the basis that her contribution didn't match his "extraordinary talent and energy." Charman lost a later appeal for a larger share.

In 2014, a judge decided that Jamie Cooper-Hohn, the ex-wife of the Children's Investment Fund Management UK founder Chris Hohn should get 36 per cent of their $US1.5 billion marital estate. She didn't appeal.

Despite rarely reaching the top courts, "special contribution" is developing into a regular tactic to employ in high-stakes divorces.

Another judge awarded the wife of 78-year-old Khoo Kay Peng, Malayan United Industries's chairman £64 million in their divorce, after 42 years of marriage. She had sought about £100 million.

The judge described Peng as a "hugely successful entrepreneur and businessman" but ruled that given the "substantial contribution" in the home made by his ex-wife Pauline Chai, "much of it on her own, on different continents from her husband," there was no case to award him more. He plans to appeal the decision.

Soccer genius?

Tuesday's ruling "comes at a time when family lawyers are following the development of the 'special contribution' argument with interest," said Jo Carr-West, a family lawyer not involved in the Work divorce case.

This week, ex-Manchester United soccer player Ryan Giggs said he plans to call expert witnesses to try to convince a judge to award him a bigger share of the estate in his forthcoming divorce case.

"It remains to be seen whether the courts think that the skill of Mr Giggs' left foot equates to the compositional genius of Mozart."

Bloomberg