This is a great question. When choosing casino, the first thing you should pay attention to is the license. If casino is licensed in the UK, they should have license from the UKGC (UK Gambling Commission), which guarantees that it is legal. Be sure to check if they use SSL encryption to protect your data. These are minimal security requirements, but they are extremely important. I would also recommend reading reviews and comments to see how honest the casino is. If you want to learn more, go to cardmates. They have the most reliable casinos for UK players. Good luck!