UK online casinos operate under strict rules set by the UK Gambling Commission...

https://wiki-net.win/index.php/What_Role_Does_Evolution_Gaming_Play_in_UK_Online_Casinos%3F

UK online casinos operate under strict rules set by the UK Gambling Commission to ensure fairness and player protection. They often offer games with a minimum 96% return to player (RTP), meaning most bets are returned over time