Well I don't know if he was "the fastest" but I have read that he practiced for 10 years to get the Hammerklavier up to that speed...But you see, (better you hear) that speed is very relative...
Ah, but how accurate was Beethoven's metronome?
According to Schiff (check out his lecture on the Hammerklavier), it's as accurate as any other. I know this is almost blasphemous, but I doubt even Beethoven played it that fast!
It's a stupid question in the first place.
Check out Rod Miller starting at 1:50.