Once, I witnessed a woman scrambling up Blaven in thin trainers - but it was in June and in good weather so hope she was lucky and returned home safe. I don't know 'cause we didn't wait for her
Seriously, the complete lack of imagination of some people makes my hair stand upright
Of course, everybody makes mistakes, sometimes even experienced climbers forget stuff or lose equipment. But charging up the Big Ben in winter in trainers goes beyond my understanding.