It's very curious because [the backwards intro] comes from the end of the song and we took it home, not being very familiar with the way studio tapes were done: it was a one-sided tape, it was a full track-tape - we thought it was a two-track tape and we thought we could take it off and put it on the other way around, and play the other side. I think Roger did this and took it home and it came up backwards and the first thing there was the gong and then all this backwards stuff. And the funny thing was that the riff is palindromic - it's the same backwards and forwards, more or less - so it sounded like the same riff but backwards and Roger, at first, thought that something had gone wrong with the tape and that the riff was still there. Anyway, it sounded so good we thought we'd put it. I think Mike did the edit - Mike Stone, our engineer who's been with us all along, and he did such a good edit, which is very difficult to splice, but he managed to get it the first time, so you can't even really hear the join because the riff is the same and it just crosses over from backwards into forwards without anyone even realising.