Yes indeed - in the case of Studland Circle - The Anglo-Saxons were just using it as a horse corral, but that doesn't mean that it was originally intended to be one.

Do we know much about the horse in prehistoric Britain? Hunted for food in the Palaeolithic, but what about in the Neolithic? Ox carts did the heavy work and oxen were used for the plough right up to the middle ages. Iron Age chariots must have been horse drawn.