Thanks for the reply! I'm not sure if we're talking about the same one. The one I'm talking about is the one that opens with the acciacatura from C# to D, with the mordent (E F# E F#) in the same bar. It was on Trinity Grade 8 at one time, and the last movement is Grade 5 or so. The suggested tempo in the old Grade 8 book is 112, and while I think this is too pedantic, it sounds like a completely different piece of music at Brendel's speed!
He certainly doesn't lose any clarity but the character is very different at this pace and I think I prefer it slower.
I actually played this for my own Grade 8 and am trailing it out again for a performance now. I probably played it at about 115 at the time for safety's sake, and can manage it faster now, but I'm not sure how far to go.
P.S. The movement ends on an F#! (RH thirds.)