Two men and a woman cheated casinos in Britain out of nearly $638,500 in a high-tech poker scam using hidden miniature cameras and earpieces, say police.

Detectives said they thought at least six casinos in the London area were targeted over a period of several months by the sting, which involved two of the gang playing poker while their accomplice sat in a van parked on a nearby street.

Using a tiny camera, hidden up the sleeve of one of the players, cards would be filmed as the croupier dealt them.

This footage was beamed live to the van via a transmitter where it was then viewed in slow motion, showing what the cards had been.

The two poker players were then told via earpieces how to bet.

"These three people executed a sophisticated system that allowed them to cheat at least one casino out of a significant amount of money," Detective Inspector Darren Warner of the Metropolitan Police's Gaming Unit said.

On the night the cheats were caught, they had netted nearly $US7,000 ($A8,900) in 50 minutes.

The scam was rumbled when casino staff became suspicious about the success of one of the gang and wondered why the same white van kept turning up outside.

Yau Yiu Lam, 45 was jailed for nine months, while Fan Leung Tsang, 41, and Bit Chai Wong, 39, were given nine-month suspended sentences and 150 hours' community service.

All were banned from casinos.