The early Children's Horse Show
Anyone who's read Diana Pullein-Thompson's I Wanted a Pony will remember Augusta going to see her cousins ride in a show, "a very posh affair with expensive cups, presented by rich and well-known people." Augusta has to watch the show with her aunt, from the car, which is parked by the ringside. Augusta escapes from the stuffy car, to her Aunt's ire: "Aunt Margaret... said that I was a queer little girl - standing amongst the crowd with the sun in my eyes, when I could be sitting in the car for which she had paid five shillings to park at the ringside."
The show, in fact, sounds rather like the Fifth All-Children's Blairavon Pony Show, for which I have an immaculate and beautiful schedule, preserved in the pages of a Riding magazine from 1938. Here it is: