Alcohol licensing laws in the United Kingdom make it so that it is against the law to sell alcohol to people that are under 18 years old. To sell alcohol legally in the United Kingdom, you must have a license - just like if you wanted to watch a movie that was rated for people 18 or older, you would need to show your ID. In order to get a license to sell alcohol, the business owner must prove that they can sell the alcohol safely and that they are following government laws. They also have to show that they are not selling alcohol to people who are not allowed to have it, like people who are still under 18 years old. So, if you want to buy alcohol in the United Kingdom, you need to show an ID that proves you are over 18 years old.