There's a great piece that explains
how tea became popular in Britain over at the Jane Austen Centre website. What interested me most was 'tea and a walking the fields', a trend the 7th Duchess of Bedford invented in the early 1800s that soon spread to all classes of society (the tea, that is).
I remember being taken to my first 'high' tea when I was still in primary school. Tea, sandwiches, and a swimsuit fashion show; trust the Asians to find the ideal way to draw in a large — and predominantly male — crowd. So I was extremely tickled to discover in this piece that 'high' tea was what the middle and lower classes enjoyed, and the upper classes (who my countrymen clearly were aspiring to be) indulged in 'low' tea:
Traditionally, the upper classes serve a "low" or "afternoon" tea around 4:00 PM just before the fashionable promenade in Hyde Park, at which one might find crustless sandwiches, biscuits, and cake. Middle and lower classes have a "high" tea later in the day, at 5:00 or 6:00.
Trust the English to outfox the colonies by inversing the connotations of high and low!