Randy Work must pay ex-wife Mandy Gray half of their fortune after the appeal court backs initial ruling that his contribution to the marriage was not exceptional

A US banker has been ordered to pay his ex-wife half of the family’s £140m fortune, after the court of appeal rejected his claim that his “genius” outshone her contribution to the marriage.

Randy Work, 49, a former executive at Texas-based private equity firm Lone Star, had first claimed that his wife of 20 years, Mandy Gray, was entitled to only £5m because she had “unfortunately” failed to stick to the terms of their prenuptial agreement and had had an affair with the couple’s personal physiotherapist.

A high court judge rejected Work’s claim that he made an “exceptional contribution” to the marriage and was therefore entitled to more than a 50-50 split of the couple’s assets, which include a £30m mansion in Kensington, west London, complete with swimming pool and fitness centre and an £18m ski lodge in Aspen, Colorado.

Ruling on their divorce in 2015 Justice Holman told the businessman that his wealth contribution – which Work said totalled more than $300m in 10 years – was not “wholly exceptional” and rejected his claim to be a financial “genius”.

“I personally find that a difficult, and perhaps unhelpful, word in this context,” Holman said. “To my mind, the word ‘genius’ tends to be overused and is properly reserved for Leonardo da Vinci, Mozart, Einstein and others like them.”

Work, who has spent at least £3m fighting to keep his wife from collecting half of the family fortune, took the case to the court of appeal which on Tuesday unanimously rejected his appeal against Holman’s ruling. “In our view the husband has failed to demonstrate that Holman J’s decision was wrong,” three court of appeal judges said.

London has become known as the divorce capital of the world because British judges tend not to discriminate between breadwinner and homemaker and order equal splits of combined fortunes. However, Work had hoped to convince the court of appeal judges to allow him to join those few men who had been granted more than half of the combined assets in a divorce in recognition of the “wholly exceptional nature” of their success.

Sir Martin Sorrell, founder of advertising firm WPP, was awarded 60% of joint assets in his 2005 divorce from Sandra, his wife of 33 years. In 2014, a judge granted the ex-wife of Chris Hohn, the billionaire founder of hedge fund The Children’s Investment Fund, 36% of their $1.5bn fortune.

Holman had ruled that although Work was an “astute businessman”, Gray was a “highly intelligent” woman who had given up her career to follow her husband to Tokyo, where he made hundreds of millions of pounds exploiting the Japanese financial crisis.

“A successful claim to a special contribution requires some exceptional and individual quality in the spouse concerned. Being in the right place at the right time or benefiting from a period of boom is not enough,” Holman said.

“It may one day fall for consideration whether a very highly paid footballer, who is very good at his job but may be no more skilful than past greats, such as Stanley Matthews or Bobby Charlton, makes a special contribution or is merely the lucky beneficiary of the colossal payments now made possible by the sale of television rights.”

Facebook Twitter Pinterest Mandy Gray, who split up with Work in 2013. Photograph: Nick Ansell/PA

Holman said Work and Gray, 47, had been “two strong and equal partners” and he would not have been able to amass his vast fortune without her contribution.

The pair, who are both American and have two teenage children, met in 1992 and married in 1995. They split up in 2013 when Gray began an affair with the couple’s physiotherapist, 44, who she now lives with in a rented flat in Kensington.

During the divorce hearing Holman had said the case “should be so easy” to settle as there was “plenty of money to go round” and criticised the couple for descending into “unedifying and destructive pugilism”.