Lothian
should be banned
If they are local they walked or used a quad bike/ motor bikes, Otherwise they drove and walked the last bit.In addition to the footpath that runs parallel to the wall at a distance of a yard or two and is part of the Pennine Way, there's one that runs south of it, avoiding the hilly bits. As the crow flies, its nearest approach to the Gap is 80 yards. The main east-west road is ⅓ mile off.
I doubt they parked on the main road as they would have blocked the lane for an hour or so. Probably parked at steel rigg a 20 min walk away.