This is a lovely site and very accessible.
The only reference to the place that I can find is by Stanhope White, who places it in the Iron Age but the vibe I get is of a henge albeit an angular henge.
What you've got is a square-ish enclosure with rounded corners surrounded by a rounded ditch the a bank with one possibly two entrances.
The dimensions are roughly 55 metres from corner to corner of the enclosure, an 8 metre wide ditch and an 8 metre wide bank with no external ditch.
The setting is a faily flat plain of fertile farmland, the are barrows in the vacinity and a set of double dykes.
I would love to know more about this site.
Conclusion - Well worth a visit, whatever it is.
Check out the multimap aerial view.
"Not far from the Percy Rigg village, on Ayton Moor at NZ598114, is a square enclosure with rounded corners; the earthen wall have been almost eroded away, but it can be seen that there had been an internal ditch. This cannot have been a defensive work, and a similar structure in a far better state of preservation exists at Studfold Ring. The name implies an enclosure for horses and the internal ditch can be seen today in many open air zoos."