The strip of metal had been badly cut giving it a serrated edge that caused it to cut into the tyre and burst it. The cut mark matched the tangled mess the strip ended up in, and it was the reason why the piece of tyre that hit the wing was so large. The tyres on Concorde were supposed to break into small fragments should they burst. Also, the screw holes had been haphazadly drilled and didn't even form a straight line which is probably why it fell off in the first place.