http://en.wikipedia.org/wiki/Legal_drinking_age
Children under 5 must not be given alcohol unless under medical supervision or in an emergency (Children and Young Persons Act 1933, Children and Young Persons (Scotland) Act 1937).
The minimum age for the purchase of alcohol is 18. People aged 16 or 17 may consume wine, beer or cider on licensed premises (pubs/bars/restaurants) with a table meal. In England and Wales, it must be an adult who orders, however an adult doesn’t have to be present to order alcohol with a meal in Scotland. The legal age for the purchase of alcohol from an off-licence (store/supermarket) is 18. (The legal age to buy liqueur chocolates is 16. but this is rarely enforced.)
Under the BBPA’s Challenge 21 scheme, customers attempting to buy alcoholic beverages are asked to prove their age if in the retailer’s opinion they look under 21 even though the law states they must be a minimum of 18. Many supermarket and off-licence chains display Challenge 21 notices stating that they will not serve persons who look under 21 without ID.
There is also a new “Challenge 25” scheme being rolled out in some parts of England, Scotland and Northern Ireland.
Purchasing alcohol on behalf of a minor is illegal in all of the United Kingdom. This means acting as the young person’s agent.