Actually the video on youtube of Bert playing this song is definitely in drop D tuning, capo-ed at either the 2nd or 3rd fret. 3rd fret to match the video. Watch the chord forms in the video, they do not work in DADGAD. I learned a DADGAD version and it sounds nothing like his. As a matter of fact, I haven't heard two versions by Bert that sound alike, so there ya go!