Is Bono having some sort of musical midlife crisis? Speaking to BBC Radio jock Zane Lowe last night, the Killiney man suggested that he and his band have a lot of work to do to hit the heights of some of their best known work.

When asked by Lowe whether it was difficult to remain relevant in the constantly fluctuating musical landscape, Bono told him: "We're [U2] 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. It that's relevant to other people, great. But we don't know."

U2 released a free-to-download track 'Invisible' yesterday for charity and Bono has said that the song is a good example of the shape that U2 are in coming into the release of their 13th record.

"We went back to why we wanted to be in a band in the first place", he said. We were listening to the Ramones and Kraftwerk - you can hear both on 'Invisible'. It opened up a whole valve for me writing, it was like a damburst of sorts."

Bono also confirmed that the band are still tinkering with the upcoming record and they should be finished in two months, also saying that he intends for U2 to undertake an indoor venue tour when it's released.

So no Garth Brooks-like four Croke Park dates for Bono and the lads then...