Crockfords, Britain’s oldest casino, is refusing to pay the world’s top poker player his $11.7 million win until they’ve completed an investigation of his game.

Phil Ivey, a California native, hit a two-night winning streak at the private Mayfair gaming club. He was playing Punto Banco, a variation of the card game baccarat.

The casino agreed to pay the winnings into his bank account, but six weeks later Ivey has only received a refund of his $1 million stake.

The casino immediately launched an investigation after Ivey left the club. Investigators interviewed everyone who was working during the two nights Ivey played and they examined hours of film from surveillance cameras, ten of which were in the room he played in.

Suspicions about the game increased after the casino discovered Ivey’s female companion, who sat at his side while he played, had recently had her membership at another Mayfair casino suspended.