Now this one shouldn't be too hard to locate!
Looking at the sign and doing a bit of detective work it would seem obvious that this is the junction at www.google.co.uk/maps/preview#!q=nenthead&data=!1m4!1...
The evidence is:
- the B6293 is now the A689 (www.sabre-roads.org.uk/wiki/index.php?title=B6293)
- the distances from that point to Garrigill and Middleton pretty much exactly match those on the sign
BUT ... why are there no houses?
So I'm now thinking it may be at a junction just outside Alston, but which one?