I recently completed a walk in the Peak District based on 'Joe Brown's Numbers'. Joe was one of the best rock climbers in the 1950's & 60's and worked for a time at Whitehall Outdoor Centre near Buxton. While there he put together a walking trail around the area based on sequential Grid References. At each of 20 locations he carved into rocks & stones a 6 figure GR which gave you the next point in a circular route. Armed with a set of clues and the the first point it was possible to do the whole circuit. Due to weathering some numbers are now impossible to read but most of them are in good condition and it has been revived by several people and made into a Geocache.
As I am based in Scotland I only had a couple of days to do it so I adopted a less pure style. I obtained GPS co-ordinates of all the locations and plotted them on a map. It provided two circular walks of about 10 & 7 miles. I completed the walks over two days just using the map and the clues but a couple were quite elusive so I resorted to the GPS (Indeed one of Joe's numbers is incorrect and I used the corrected figure).
I can thoroughly recommend it as an outing and would be interested to hear if anyone else on UKC/H has completed this walk.
In reply to Wingnut:
The inscription at the barn has now weathered beyond legibility but the guy who set up the geocache has placed a laminate with the numbers on it very close by. The bog is no less fearsome!