As Don mentions below, by scanning where the ball passes a fixed point 2 or 3 times, apparently you can predict which quarter of the wheel the ball will fall. Not specific of course, but like card counting in blackjack, it just tips the odds from 3% house edge (remember roulette in the UK is always single zero so a lower edge to start with) into a small edge for the player. With the Ritz taking large bets, a big profit is quickly possible.

I'd just be happy to have the opening stakes that these guys must have used

Jason