The One hitmakers shot to international stardom in the 1980s and maintained their status as one of the biggest bands in the world throughout the 1990s.However, their most recent album, No Line on the Horizon, was released five years ago and singer Bono worries the band is no longer of interest to music fans.Speaking to Radio 1's Zane Lowe, he says: "We're on the verge of irrelevance. You have to make stuff relevant to you and where you're at, make an honest account of what you're going through - if that's relevant to other people, great. But we don't know."We were trying to figure out "Why would anyone want another U2 album?" And then we said "Well, why would we want one?""We'll find out if we're irrelevant. I'm perfectly prepared for people to try and blow us off the stage. We're just not going to make it easy."