DUBLIN — A legendary Irish gambler took a celebrity-obsessed American private equity honcho to the cleaners, winning over $17 million from him in the course of a 72-hour backgammon session.

Had he been Irish, Alec E. Gores, who nurtures friendship with celebrities such as Sylvester Stallone, Tobey Maguire, and Ben Affleck, and was caught up in the Anthony Pellicano wire-tapping scandal after he apparently set the private dick on his wife who was having an affair with his brother, might have known better than to get into a game of chance and skill with JP McManus.

The Irish racehorse owner started out as an on-course bookmaker, but went on to amass a property and bloodstock fortune worth over $50 million when he switched from taking bets to making them.

McManus is famous for traveling with a portable backgammon set and, sources acquainted with him tell The Daily Beast, has been known to start games with strangers on airplanes in a (usually successful) attempt to win back his airfare.

But when he sat down with Gores, who is worth $2.1 billion, in November 2012 for what has been described as a “serious backgammon match” he walked away with enough to buy not a plane ticket but a private jet—his winnings were a stunning $17.4 million.

The details of the marathon gambling session emerged in court papers, which have been filed by McManus, who is bringing a case against the IRS.

Gores withheld $5.22 million of the winnings, and paid them to the IRS to cover potential federal tax liabilities. But McManus’s lawyers argue that this amounts to “double taxation” on his income as he pays a substantial annual levy on his income to the Irish authorities.

His lawyers say that, as he is paying his tax in Ireland, he should be refunded the money by the IRS under a 1997 tax treaty between Ireland and the U.S.

Friends of McManus told The Daily Beast there was “no way” the legendary punter would let the matter drop.

“JP is not the kind of guy to roll over and say, ‘Oh, forget about it.’

“Don’t forget JP started with basically nothing. His fortune stems from a £4 bet made when he was 20 in 1970.”

McManus famously bet £4 on Linden Tree in a British horse race in 1970, winning £50 when the horse won at 100/8. He staked another £4 on the same horse in the Gold Cup, a bet which returned £100 when it came in at 25/1.

According to a report in the Irish edition of (paywalled) British paper The Times, McManus’s lawyers are arguing that the IRS are seeking to, “improperly confiscate McManus’s money under the guise of twisted legal reasoning.”

McManus is famously retiring when it comes to media interviews, but he did once talk to a local Irish newspaper, the Limerick Leader, in which he gave an insight into his mentality and modus operandi:

“I’d bet on anything if I could find someone to bet with me,” he said, “But looking back, and as a friend pointed out to me, you change the addiction to gambling to one for winning. It’s not the gambling that’s important, it’s the winning.”

McManus added, “If you can change the addiction, you become more controlled, more conscious. You have to have discipline and temperament.”

Asked if he was a potential case for Gambler’s Anonymous, he replied, “I don’t know about Gamblers Anonymous, don’t know much about it. I just know I had a gene in me and I wanted to gamble all the time. But I was very lucky, when I started gambling on the racecourse. One, I didn’t have a family history going into it. That can be an advantage in that there were no old-fashioned ideas. Maybe we were the start of that new group who believed they could make punting pay. And I saw, as a bookmaker, punters who were very regular winners. They weren’t big gamblers, but they fed their families, sent their kids to college. You’d find you were writing them the check every Monday.”

Gores is no stranger to high-stakes gambling—Forbes detailed another legal suit which revealed that in a weekly poker game attended by Gores and former Spiderman star Tobey Maguire, he won $445,000.

Gores was dragged into the Pellicano case after court filings showed the shady private eye was involved in surveillance on his former wife.

According to The New York Times, “Mr. Gores, principal of the private equity firm Gores Technology Group, admitted hiring Mr. Pellicano in 2000 to investigate his suspicions that his wife was cheating on him with his younger brother, Thomas.”

The New York Times added, “Mr. Pellicano installed wiretaps on both Lisa and Tom Gores’ telephones, the summaries show, and confirmed Alec Gores’ suspicions that the two had become inappropriately involved.”

Gores was not charged with any wrongdoing in the case.

For Gores, it seems, the loss of $17 million was just a bad day at the office. McManus, however, is unlikely to be so blasé.

“He’s rich, but not so rich that he wouldn’t notice two million quid,” says the friend. “Anyone who knows JP knows he’ll leave no stone unturned to get that money back.”