The summit of Grey Nag (near Alston) - Cumbria to the left, Northumberland on the right of the wall.
Burnhope Seat - the old county top of Durham - which overlooks Weardale
Three Pikes (between Weardale and Teesdale) - an oddly named hill. There are no pikes and there is just one hill. But there are lots of peat bogs. YC suspects that only dedicated peak-baggers made the trip to this hill.