The road dips into the valley of the stream which flows on to form the lake in Grimsthorpe Park. Just skirting the glacial till, it rises to the crest at the other side, on the Kellaways clay and sand and turns sharply left onto the till. It used to go straight on and pass the north front of Grimsthorpe Castle. When the soil in the field beyond the bend is bare, its course can still be seen. The castle's owner did a deal with the turnpike trustees. He brought land on the other side of the road into his park and built them a new, though longer road around it. Once the semi-circular diversion is completed, the road turns sharp left again, through Grimsthorpe where it is on Jurassic clay. The 1824 Ordnance Survey map shows both the old and the new roads.