A laser scanner was allegedly used by the gamblers

The trio - a Hungarian woman and two Serbian men - were arrested in March but police have apparently decided that they did not break the law.

A laser scanner linked to a computer was allegedly used to gauge numbers likely to come up on the roulette wheel.

But police said the case had now been closed, with no charges brought.

The gamblers managed to earn £1.3m in winnings thanks to the alleged "sting".

On the first night they won £100,000 and on the second took home another £1.2 m, the Sunday Times reported.

Funds frozen

They allegedly used the scanner to judge the speed of the ball on the roulette wheel and hence the number most likely to come up.

The paper reports the gamblers were able to do the calculations swiftly enough to place their bets as required before the roulette wheel has gone round three times.

The three were arrested after the casino launched inquiries and initially their funds were frozen.

The newspaper said casinos throughout the country were examining security as a result of the case.

A spokeswoman for the Ritz Casino said they had "no comment" to make on the case.