In Gibraltar:

According to the Children and Young Persons (Alcohol, Tobacco and Gaming) Act 2006, persons aged 16 years and over alcohol may be served provided the alcohol is:

• beer, wine or cider and is of an alcoholic strength not exceeding 15%;
• sold in, or poured from, a pre-packaged container and is of an alcoholic strength not exceeding 5.5%
• the alcohol is sold for consumption on licensed premises or
  
• the alcohol is procured for consumption by and under the  supervision of a person who  has parental responsibility  for the relevant person (a “parent”) or is 18 years.

Any person who sells alcohol to a person under the age of 18 years (and failing to meet the criteria above) is guilty of an offence and is liable on summary conviction to a fine up to level 5 on the standard scale.

In the UK:

• At 16 years of age beer, wine and cider can be consumed on premise if taken with a table meal and when accompanied by an adult aged 18 or over
• At 18 years of age you are allowed to consume alcohol in pub, bars and restaurants.