We can't be sure that it was part of the original circle, we read one account that regarded it as a porthole entrance stone that had been removed from a chambered cairn and inserted here later. What is certain is that either the ring or the two stones have been moved since 1745. Borlase's plan shows the three upright stones set in an arc (perhaps the circumference of the stone circle?) but the ring is set at 45 degrees to the circumference, not in a radial or tangential position as would normally be expected.

Pre-concrete, assuming the hole was always left unburied, it was probably fairly easy to topple and given the healing legends associated, it has probably been over a few times in the far past.