Bettors always want to be playing with the best payout casino, but the sheer amount of casino sites available in the UK can make it difficult to determine the cream of the crop.However, by using the return-to-player - or RTP - metric, bettors can work out the best payout casinos available in the UK.Here, we compare the best online casinos that publish their genuine RTP figures and carry the deepest high return-to-player game catalogues across slots, table games and video poker.What is RTP?Return to Player, commonly shortened to as RTP, is the percentage of every pound staked on a casino game that is statistically designed to pay back to players over millions of spins or hands.So, a 96% RTP slot returns - on average - £96 in winnings for every £100 wagered over the long run. The remaining £