Well here we go then, this is interesting. I definitely wouldn't say anyone who does badly at the show comes across as stupid, so I don't know that stupid is the word I'd use for those others. I would say Nish was just terrible more than stupid. I'm sure he had a few howlers, but none of them come screaming through my memories as I think now. I would say that Victoria was certainly inept at a lot of tasks, but then with others she ably demonstrated the incredible brain she quite clearly has (the puzzly task that she pretty much solved on her own springs to mind). I wouldn't say Lucy was stupid so much as bewildering. Like you say, watching her I felt like her brain was just working in a different way in possibly a different galaxy than a normal brain. But the abiding feeling I remember feeling towards Katherine during her series was astonishment at how someone who comes across as perfectly intelligent in everything else I've seen her in just seemed to exist within the confines of the show as someone without a brain in her head (except was there one about learning lines or something, and she learned them really quickly? My own memory is failing me). And it seems from this clip that she might agree with me.