Bono has confessed U2's latest world tour was under threat just weeks before it kicked off in San Diego, California - because they were sounding so bad in rehearsal.
The rockers opened their Vertigo roadshow last month and scored rave reviews for their dynamic performance.
He says: "It's still a strange feeling. We were sick with the rehearsals for this tour. We weren't getting lift-off. If you'd seen the rehearsal show, you wouldn't believe we would get to San Diego.
"You take all these different elements and try to create something special. And when we got up there, we were lucky and we got it straight away. But, you know, this is a tour we didn't even know was going to happen."