The two feats of endurance, here in my home country of Wales, that i find most impressive, was John Wagstaff, of West Bromwich, June 1978 Triple Welsh 3000s traverse, all in under 22hrs.
The other, is Nicky Spinks 57hr double traverse of the Paddy Buckley round, a dizzy 122miles over the roughest terrain, here in Snowdonia.