The cache is NOT at the posted co ordinates.
Stage 1: Use your OL28 1:25000 map
At the Hameldown Tor triangulation point, you head downhill toward the nearest road which you follow until a path leads off to the west. You take the path until it reaches another road; you head down the road to the pub. A track beside the pub leads you uphill where you stop at a cairn. To your north, you can see the wide expanse of the forest and decide to skirt the westerly edge, crossing two small streams on the way. A track is apparent to your left, so you follow it past two stone circles and down toward a river. A footbridge crosses the river, so you make your way to it. Which OS grid square are you now in? Grid = ABCD
Stage 2: Visit the trig point and obtain the four digit number from the base plate. Trig No = EFGH
The cache can be found at:
N 50 (C-G) A . (B+G) (E+B) (G-E)
W 003 G (B-E) . D (G-D) (D+B)
