Obviously, if you go back to the 19th century there was a stack of it, as there was no minimum drinking age until 1886. Even then, legal age was a pretty liberal 13. The current age of 18 was only introduced during WW I.
Between the wars there seems to have been little underage drinking. Which may have had as much to do with the economic situation as it did with a desire to stick to the rules.
While during my youth, it was rampant. Pretty much everyone I knew was drinking in pubs by the age of 15. There seemed to be an unwritten rule that you could drink in pubs from around the age of 16 or so, as long as you didn't behave like an idiot. I was never once refused s drink while underage.
WW II changed the interwar situation. And money seems to have been one of the key factors driving youth to drink.
"Drinking Among the Young
A letter in The Times of 23rd February, signed by the heads of six famous London settlements, urges licensees not to serve boys and girls under 18 with intoxicants. Here is an appeal that will not fall on deaf ears. We may be sure that licensees will be sympathetic. Indeed, they will be encouraged by this letter in the hope that support will come from unexpected quarters. Nobody likes the common informer. But if the skilled and humane staff of these settlements would collaborate in what is a truly serious problem by giving licensees a hint that this or that boy or girl is trying to buy intoxicants, nothing but good could emerge.
For, indeed, this is one of the plagues of a publican’s life. The young have money burning in their pockets; they have been working side by side with grown-ups; they want a fling and they mean to have it. In understaffed and overcrowded houses the fling may well be easy, at least once or twice—but perhaps not again. Anyone who shops nowadays or uses a garage or any trading establishment knows that he will probably be served by a child; but whether that child is seventeen and three-quarters or eighteen and a quarter only a birth certificate could show. And now that girls of 16 or 17 dress to look three or four years older, now that hair is neither “up” nor “down,” it must be recognized that the overworked publican requires a genius for discrimination. A recent report from Liverpool contained an example of the other side of the problem : “I heard of one young woman who was several times refused alcoholic drink and was later found to be a married woman of 34 with the appearance of a girl of 16.”"
The Brewing Trade Review, March 1943, page 64.
The trouble of correctly the age of girls is just as true today.
It was probably the first time that the bulk of Britain's youth had some disposable income. The irony being that there was bugger all for them to spend that cash on. With pretty much everything either rationed or in short supply, options for spending were limited.
While they might have been loud down the pub, the underaged weren't pissheads:
"Recent reports from a dozen great provincial centres agreed that drinking among th
e young, however noisy, was not the same as drunkenness. Miss Violet Markham’s Report on Amenities and Welfare Conditions in the Three Women's Services confirmed an absence of drunkenness. In four strikingly original articles in The Times Educational Supplement Dr. Macalister Brew recorded the result, in her search after knowledge of how the young spend their leisure, of a 100 visits to public houses. She concluded that they went to the public house for sociability rather than drink. They went to talk—“ and how they talk!” She analysed the subjects: the most popular was “some aspects of rationing (including clothes), the next most popular was “ religion (how to lead a good life, general aspirations, etc.).”
Yet the absence of rival peace-time distractions, the novelty of wages without knowledge of the value of money, and the sheer desire for a lark have placed a heavy new burden on the licensee. And in his efforts to avoid serving the under-aged with intoxicants he needs sympathy and help. The letter in The Times points the way."
The Brewing Trade Review, March 1943, pages 64 - 65.
Was religion really that popular a topic of conversation among the young? I struggle to believe that.
The pub has always been as much about sociability than getting plastered. Otherwise, why not just sit at home with bottle of cheap vodka?.