Thanks to all who replied. When I went back I had my metric socket wrench with me, and between the proper tool on the nut on top (8 mm) and lots of finger tip pressure below, I got it off. The thread is 5 mm and the bolt head is 8 mm too. The bolt is 30 mm long (available at the local hardware store); the (missing) bolt which clamps the bracket tight on the pedal is 40 mm but the hardware store only had 30 mms and 50 mms. Hopefully there's enough space for the extra long bolt; otherwise I'll whip out my hacksaw. Thanks, Patrick
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