U2 are already hard at work on their next album Songs Of Experience.

The follow-up to Songs Of Innocence, which was released earlier this month, is 70% complete, according to bass player Adam Clayton.

He told Q magazine: 'I think we've probably got 70% of the material that we think will go onto it.

'The 30% that we're missing I think we'll be able to generate relatively easily. But the amount of energy it will take to refine the perspective of those songs is hard to predict.'

The band will officially release Songs of Innocence on October 13, after giving the album away to iTunes users earlier this month. Bono has revealed U2 are planning an arena tour for 2015.