For British - 18 years old.
I went to Pub when I was 16 years old but I look older than 16 years old...
But here in Germany is different as British.
The children are allow to go in Pub anytime as long as they are under their parental´s supersivon.
German law: Teenagers are allow to drink beer and wine at age 14 and spirits (Gin, Vodka, etc.) from 18 years old.
Not here, anyone under 21 who drink or anyone who serve them get ticket, big fine $$$$$$$$.
Sorry, it is off subject.