“Edge is the archaeologist of the band, he’s the Mother Teresa of Lost Songs. We had kind of forgotten the genesis of Atomic Bomb and Mother Teresa himself found it with these songs. We’re all so grateful because these songs have a spontaneity that some of the best recordings on How To Dismantle An Atomic Bomb have, it’s fresh paint without any added layers or the second or third guessing. Which can happen – we do tend to second or third guess ourselves.

“It’s a band, everyone has a view. If we had to put the song or album out the following day, decisions would be clearer… but sometimes we move on too quickly and some real beauties can be left behind.”

Not for the first time, Bono is thanking Edge for spotting something in U2’s vast studio output that may have previously eluded Adam, Larry and himself. In this case it’s the merits of the songs that for various reasons were left off 2004’s How To Dismantle An Atomic Bomb, but which – revisited for the album’s 20th anniversary – sound as fresh and vital as the 11 tracks that did make the final cut all those years ago.

As well as adding to our understanding of what was going on in U2’s minds between their Elevation and Vertigo tours, this – as they describe it – ‘shadow album’ drops heavy hints as to what we can expect next from the band.

“It’s so relevant to a lot of music that’s going on now,” Edge says in relation to both the original Atomic Bomb and its new companion. “In our country, there’s a resurgence of punk rock. I was watching a young band play live called Shark School and there’s another punk band from the west of Ireland, 50 Foot Women. Kids in their teens and early twenties. Really, it’s all of the energy of this collection of songs. It’s of the same spirit and primary colours – guitar, bass, drums, vocals.”

Along with the thrill of those primary colours, Edge touches on something else.

“There’s room to expand and be more ambitious in lyrics and songs,” he reflects. “This is the moment. A return to the importance of lyrics, to the point of where it was back in the early ‘70s with Leonard Cohen, Lou Reed, punk rock, the Stooges. There were some amazing lyrics in those days and I miss it.”

As for what’s been on the Hewson hi-fi, Bono reveals: “Presently I’m listening to epic Irish ballads, I’m paying extra attention to the storytelling that’s at the heart of great folk music. The details of character and geography as well as the usual emotional landscapes. But no crying in our beer here. Rock ‘n’ roll – whatever it is these days – deserves its day in the sun.”

The suggestion, if you combine Edge and Bono’s testimony, being that U2 are eager to reacquaint themselves with the band’s punk rock roots – and their complex Irish DNA.

“Edge has likened Re-Assemble to a throwdown, in terms of where U2 might go next,” the latter resumes. “I want to hear the sound of our band in a room. To feel a performance get away from us and be better for that. I experienced that last month (in the rehearsal room) with Larry. Adam and Edge and I want more.

“I want to match Edge’s melodic flights with a more earthbound lyricism that might be required to negotiate these modern times. How To Re-Assemble An Atomic Bomb, in its directness, is certainly an inspiration for us now as well as then. It won’t inform all our music, but right now we’re all about the moment. And if you want to live in the moment you have to be ready for it… fit for it. There’s no hiding, it’s very demanding. I would say Edge, Adam, Larry and I are in violent agreement on this, and we rarely agree on anything.”

While How To Re-Assemble An Atomic Bomb offers some welcome reflection, U2’s gaze, Bono says, is now firmly focused on the future.

“You’ll never have to listen to me raging and whinging about my mother or my father ever again,” he promises. “Though I have this opera coming out, haha!”