It's no consolation but if you look at the browser and zoom to where Durham and Northumberland and Cumbria meet there is something called the Mare and Foal. There's a one digit error in that map reference and so it's in the wrong place.

I've found more bits of the Mare and Foal nearby, which I've called the Mare and Foal outlier (though it's probably the other way round) and that's in the correct place on the map. There are more bits to find as well - stones half a mile away and so on - and this whole area is neglected by megalithic explorers.