just short of two inches long. Found in thick grass on a boggy mountain
No interactions present.
... looks much more promising! I don't know caterpillars well enough to confirm it 100% but it seems a good match. See photos on the ukleps site (scroll down the list to find Scarce Umber):
By rights it ought to have been in a tree or shrub, but could have dropped from one if there were trees in the vicinity.
Entomologist and biological recorder
Lat/Lng: 52.5477, -3.0422
OS grid ref: SO294949
Found near the summit of Roundton hill fort