It's been nearly five years since the release of U2's last studio album, How To Dismantle An Atomic Bomb. But that should be no great surprise: over the course of a career spanning three decades, the band have released only 12 studio albums - and four of them within the first five years. Since the release of The Unforgettable Fire in 1984 U2 have paced themselves on the laps between recording studios - and the lengthy gestation of No Line on the Horizon was no different.

'We'd invited Eno and Lanois to come in as writers." recalls Adam, of the early thinking behind the new record. 'It was a big step up for us to say, 'We wanna open the thing up and that will determine the direction.' The band, he explained, wanted to see if the music could come from another place too - so why not try North Africa?

'Initially,' adds Larry, of the sessions writing with Eno and Lanois in Fez , Morocco. 'The idea was to do this esoteric thing and have a few hits there as well. It's kind of morphed into something else. I think there is experimentation in there... it's just a different animal. It's not quite what people would expect a U2 experimental thing would be. I mean, if you think of Zooropa, or Passengers, this is not that. This has got a lot of weight... I think it's some of the best music we've ever written.'

Setting up studio in the courtyard of a converted Riad in Fez was an inspired move in the story of 'No Line on the Horizon'. But that was eighteen months before the album release and there followed multiple recording sessions in Dublin, New York and, finally, six weeks in London at Olympic Studios. In the downtime, Adam often fished his camera out and kept short video diaries for U2.Com. Like this one.

The odd recording even sneaked out early, like this very fine acapella cover version .

But by December 2008, with Steve Lillywhite joining them in the studio - the man who produced their first three albums and helped complete the arrival of several others - they finally wrapped it up. 'It doesn't sound like anything we've done before, ' explained Edge. 'And it doesn't really sound like anything that's happening at the moment...' But the influences of the entire recording journey remained present. Take 'Stand Up Comedy':

'It started out with this very Moroccan-influenced rhythmic thing. And it's interesting that it's gone from North Africa to rock'n'roll - and in that process you really see how connected they are, the music of Africa and the United States. It's all there.'

The first track everyone got to hear was Get On Your Boots, the single, with the graphically startling video execution from French film maker and artist Alex Courtes. And as reviewers got to hear finished material, a sense of what this eleven-track, fifty three minute long player might be about began to emerge.

Brian Eno, co-writer with Daniel Lanois of several tracks, as well as sharing production credits, has been in scores of studios to witness the arrival of hundreds of songs. But he called 'Moment of Surrender', the third track, "the most amazing studio experience I've ever had".

"Apart from some editing and the addition of the short cello piece that introduces it, the song appears on the album exactly as it was the first and only time we played it."

White As Snow, was described in one newspaper as 'U2's most intimate song'. 'The song's melody is based on an old hymn, Oh Come, Oh Come, Emmanuel, that, according to The Handbook to the Lutheran Hymnal, was composed by "an unknown author, circa 1100". The idea of a song based on the dying thoughts of a soldier initially came to Bono after he read William Golding's ambitious novel, Pincher Martin, which is told from the point of view of a British sailor who appears to have survived the torpedoing of his ship. As he approaches death, his thoughts roam back over his life, and the moral choices he made or avoided....

Several of the songs, Bono explained, were written in the third person. '..I allowed myself to wear the clothes of characters that wandered into my imagination. So the guy in (new song) 'Cedars of Lebanon' is a war correspondent. I meet a lot of them in my other life. And I have a lot of empathy because I'd probably be one (laughs). And then there's this song that is called 'Tripoli' at the moment, which is this guy on a motorcycle, a Moroccan French cop, who's going Awol. He drives through France and Spain down to this village outside of Cadiz where you can actually see the fires of Africa burning...'

That song was eventually called Fez-Being Born and it's streaming right now, along with the rest of the album. As we write people are saying all sorts of good things about the record, like it's their finest since Achtung Baby.

Meanwhile, the band are out there playing the new songs. which is what they started the whole journey for in the first place.