Safety standards in the equestrian sports have certainly improved over the years! As seen in this photo from the 1983 Royal, hunter riders continued competing in top hats over fences. Mandates for helmets were enacted at various times depending on the governing body, but these mandates mostly came into effect in the early- to mid- 2000s. It is easy to forget that approved helmets weren't required at high-level hunter-jumper competitions until just over a decade ago.
Royal Agricultural Winter Fair Archives