We had played a continuous chord - me scraping away full blast on the guitars, Roger hitting as any cymbals as he had in his reach, and then we did a mix of the piece on to quarter inch tape. Then we played it backwards, and I varispeeded the machine at the precise moment downwards to a stop, copying on to another tape. Then we turned the result back around and spliced it (literally, with sticky tape) into the master mix. It was a tricky edit - and of course once you had cut the tape in those days it was hard to re-do it! But we crossed our fingers and it worked first time. As I remember it was in Sarm East studios, in the East End, and Gary Lyons was nominated to do the surgery!!! He did good!!!