GAMBLERS who adopt a well-known probability strategy to beat the house at blackjack beware – UK researchers have developed an automated system that will detect card counters before they can cash in.

Card counting, a strategy made famous by the film Rain Man, involves remembering which cards have been played, and which might be likely to turn up. An abundance of low-value cards in the discard pile can tip the odds slightly in favour of the gambler, and a card counter bets big only then.

The strategy isn’t illegal, but casinos will move suspected card counters to a new table, where …