Drinking alcohol is not in itself illegal, but particularly where young people are concerned, there are several ways you can fall foul of the law through drink. 

For example, it’s illegal to give an alcoholic drink to a child under five years old except in certain circumstances (e.g. under medical supervision).

Children under 16 years of age must be accompanied by an adult in a pub.

It is against the law for anyone under 18 to buy alcohol in a pub, off-licence or supermarket or on-line. It's also illegal for a person to buy alcohol for someone under 18 except where that person buys beer, wine or cider for someone aged 16 or 17 to be drunk with a table meal in a pub or licensed restaurant while accompanied by a person over 18.

The police have the power to stop a person and confiscate alcohol in a public place if they reasonably suspect the person to be under 18 years of age (or it is likely in the circumstances to be consumed by a person under 18) . Those under 18 who persistently drink or possess alcohol in a public places may be prosecuted.

Anyone over 18 can buy and drink alcohol legally in licensed premises in Britain. But, a lot of shops operate a scheme called Challenge 21 where if you look under 21 (or 25 in some places) and don’t have proof of your age they can refuse to sell you alcohol.