We went in and recorded exactly where we were at that point in time. I think because of the quality of musicianship of the band has given it the longevity. I thought the music would endure, I didn't think I would ... I always thought I'd be dead by 30, then dead by 40 and on and on. Now I'm 55 so I didn't even die at 50.

The idea of a hypnotic riff as the prime mover of a piece of music has been around for a long time, whether you're talking about the Delta blues or music from Middle Eastern and African cultures.

But to put out a greatest hits on one CD was totally impossible, I just couldn't do it. The best compromise was to put out two CDs - Early Days - which is what it is - and Latter Days.

There will be a Led Zeppelin as long as there's a Jimmy Page, John Bonham, John Paul Jones and Robert Plant. This isn't a nostalgia band playing the hits forever. If anything ever happened and somebody left - which I really can't see happening - I don't think we'd bother to carry on. The magic for me is as it is now.

You can't overthink the music. Mood and intensity can't be manufactured. The blues isn't about structure; it's what you bring to it. The spontaneity of capturing a specific moment is what drives it.

When I started doing sessions, the guitar was in vogue. I was playing solos every day.

There is no way I would play guitar like a tour de force like I did in Led Zeppelin. John Bonham, phenomenal drummer, young man with his technique, but do you think he would ever have the opportunity to play like that in another band? Of course he hadn't.