His body is said, on doubtful authority, to have been buried honourably by the monks of Abbey Cwm Hir, near Rhayader.
It was with the expectation that he might, with local aid, seize the castle, that Llewellyn invaded this district in December 1282, when he was surprised and killed by Stephen de Frankton in a ravine called Cwm Llewellyn on the left bank of the Irfon, 22 m.
Drws (the door of) Ardudwy, Rhinog fawr and Rhinog fach (cliffs); an exception is the verdant Cwm bychan (little combe or hollow).
Here also Owen Glendower unfurled the banner of Welsh independence; from here, in 1401, he harassed the country, sacking Montgomery, burningWelshpool, and destroying Cwm Hir (long "combe," or valley) abbey, of which some columns are said to be now in Llanidloes old church..
Cwm, a low valley, Anglicized into " coomb " - Cwm Gwendraeth, Blaencwm.