'Evidence-based' Beethoven

In an essay in The Guardian, Roger Norrington, the British conductor who produced shock waves 20 years ago with his period-instruments, historicaly informed performances of the Beethoven symphonies, restates his case for Beethoven with "pure tone" and adherence to the composer's still-controversial metronome markings:

http://www.guardian.co.uk/music/2009/mar/14/beethoven