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

https://www.cast-bookmarks.win/uk-online-casinos-operate-under-tight-rules-set-by-the-uk-gambling-commission

UK online casinos operate under strict rules set by the UK Gambling Commission to protect players. They often offer games with around a 96% return to player (RTP), meaning the house edge is built into game design