Top poker player Phil Ivey has lost his High Court case against the owners of London's Crockfords Club over his £7.7 million winnings.
The 38-year-old American sued over a version of baccarat known as Punto Banco which he played at the Mayfair casino over two days in August 2012.
After four sessions, Ivey was told the money would be wired to him and he left for the United States, but it never arrived, although his stake money of £1 million was returned.
Genting Casinos UK, which owns more than 40 casinos in the UK including Crockfords, said the technique of "edge-sorting" which Ivey used - which aims to provide the customer with an element of "first card advantage" - was not a legitimate strategy and that the casino had no liability to him.
Its lawyers told Mr Justice Mitting in London that Ivey's conduct defeated the essential premise of the game of baccarat so there was no gaming contract or constituted cheating.
A spokesman for Crockfords said later: " Crockfords is pleased with the judgment of the High Court today supporting its defence of a claim by Mr Ivey.
"It is our policy not to discuss our clients' affairs in public and we very much regret that proceedings were brought against us. We attach the greatest importance to our exemplary reputation for fair, honest and professional conduct and today's ruling vindicates the steps we have taken in this matter."
Speaking through a spokesman, Mr Ivey said: " I am obviously disappointed with this judge's decision. As I said in court, it is not my nature to cheat and I would never do anything to risk my reputation.
"I am pleased that the judge acknowledged in court that I was a truthful witness.
"I believe that what we did was a legitimate strategy and we did nothing more than exploit Crockfords' failures to take proper steps to protect themselves against a player of my ability.
"Clearly today the judge did not agree."
Lawyers for Mr Ivey were refused permission to appeal although they can renew their application to the Court of Appeal directly.
Ivey's counsel, Richard Spearman QC, told the court th at edge-sorting involved nothing more than using information that was available to any player simply from viewing the backs of the cards which the casino chose to use and making requests of the casino - which it could accept or refuse - as to the manner in which play was conducted.
The casino's counsel, Christopher Pymont QC, said that Ivey, who lives in Las Vegas and is described on the World Series of Poker website as "arguably the best poker player in the world", was not a well-known advantage player at the time of his visit but was, in their eyes, an old VIP customer and they trusted him accordingly.
It argued that edge-sorting was not a widely known or practised way of playing baccarat in the UK.
Ivey, who was accompanied at Crockfords by another professional gambler, Cheung Yin Sun, who introduced him to edge-sorting, said cheating was anathema to advantage players like him.
"We observe the unwritten doctrine: how do I find a legal way to beat the house? Any method that could amount to cheating would breach the doctrine and cause you to be ostracised by your fellow players - we are all very careful to stay the right side of the line and we discuss advantage play strategies at length."
He said he was very angry when he heard the casino would not be paying out his winnings: "I was upset as I had played an honest game and won fairly.
"My integrity is infinitely more important to me than a big win, which is why I have brought these proceedings to demonstrate that I have been unjustly treated."
In his ruling, the judge said that the case turned on whether there was cheating: "If Mr Ivey cheated, he is not entitled to recover his winnings. If he did not, he is."
What Mr Ivey and Ms Sun did was to persuade the croupier to turn some of the cards in the dealing shoe to permit them to know that they were or were very likely to be sevens, eights or nines, and in circumstances where she did not realise she had done so - and, if she had, would have immediately stopped play.
The fact that Mr Ivey was genuinely convinced that he did not cheat and that the practice commanded considerable support from others was not determinative of the question of whether it amounted to cheating.
Mr Ivey had gained himself an advantage and did so by using a croupier as his innocent agent or tool.
It was not simply taking advantage of error on her part or an anomaly practised by the casino for which he was not responsible.
He was doing it in circumstances where he knew that she and her superiors did not know the consequences of what she had done at his instigation.
He concluded: "This is, in my view, cheating for the purpose of civil law."
Dismissing the case, with costs, he said it was immaterial that the casino could have protected itself by simple measures.