The 70-year-old guitarist, who was a founding member of the group, also made up of singer Robert Plant, bassist and keyboard player John Paul Jones and late drummer John Bonham, and claims he knew the group were going to be a success.
He told The Sun newspaper: ''Every musician dreams of being in a group like Led Zeppelin,'' he raves, his dark eyes lit up.
''I was really fortunate to be a founder member. And I knew absolutely from our first album, it was going to be massive. The group was fantastic and we could deliver in live situations.
''We played as a band, each and every one of us... as opposed to one superstar surrounded by other musicians.''
The band are now reissuing their nine studio albums from June 3, with each disc matched to a second set with different versions and lost outtakes for die-hard fans.
Jimmy admits he became slightly obsessed with making sure the reissue campaign was worth it by going through all of the Led Zeppelin archives for new material and he ''left no stone unturned.''
He explains: ''I didn't want material from the companion discs to be poo-pooed with someone saying, 'Right, oh well, it's actually on a bootleg already. It's available'.
''So I asked a fellow who listens to bootlegs. That was a test. I thought he might say, 'Well, 60 per cent unheard'. But he said, 'I haven't heard any of it'. I thought, job well done.''
Jimmy insists he knew the project was the right thing to do because in five years' time people will look back at the releases.
He added: ''They'll be comparing takes and considering them to be a major part of the whole structure.''
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Pratchett died aged 66 in March 2015.