U2 released ‘The Fly’ on 21 October 1991. Bono called it “the sound of four men chopping down The Joshua Tree.” Unusually for him he was underselling things. It’s the sound of four men cutting down that tree, jamming it into a garden shredder, dowsing the shredder in gasoline and then dancing around the pyre, naked. It’s the sound of a band celebrating their own salvation, toasting an unlikely three-point turn out of a creative blind alley.

When the parent album arrived a month later, the world devoured it even if it could scarcely believe this was the same crowd who stood po-faced and be-stetsoned in the desert only a few short years earlier. Achtung Baby was, against all the odds, a sexy, groovy, multi-multi-million selling bastard that gave the band reason to continue, but it could have gone the other way.

Bono declaring that they had to go dream it all up again was one thing, but how do you follow through? If you knock down your house to build a new house, for a while there you’re going to have nowhere to live. Larry Mullen in particular thought Bono was talking a good game without the songs to back it up.

The anniversary multi-coloured vinyl reissue is such a desirable objet d’art one would nearly be afraid to take the plastic off but it is the extended digital boxset that offers some illumination, in amongst enough remixes - I'm partial to the Tabla Motown remix of 'Mysterious Ways' and the Soul Assassins rejig of 'Numb' but all that jumping around is a bit unseemly at my age - to start your own nightclub, on how they got from there to here. U2’s first release after Rattle & Hum was a 1990 recording of Cole Porter’s ‘Night And Day’ for the Red Hot + Blue compilation album. At a push, one might argue for ‘God Part II’ as their first step in the new direction, but the industrial hum and clatter of ‘Night And Day’ was a neon arrow, lighting their way. Also gathered here is ‘Alex Descends Into Hell For A Bottle Of Milk/Korova 1’, which originally surfaced as the flipside to ‘The Fly’ although it – a combination of two larger pieces – had been composed and recorded by Bono and The Edge in 89/90 for use in a Royal Shakespeare Company production of A Clockwork Orange, the research for which had first sent The Edge into the harsh industrial arms of the likes of KMFDM and The Young Gods. When, at the two minute mark, the processed beat kicks in, we’re off to somewhere new.

U2 worked first in STS Studios in Dublin, trying to find a way in, and the title of the rollicking ‘Where Did It All Go Wrong?’ may not have been ironic. They famously headed for Berlin to soak up some of that Bowie/Hansa magic but inspiration was on a vacation until they took some bits and pieces from a song called ‘Sick Puppy’ and came up with ‘One’, in about half an hour. Despite the gift of this perennial, the importance of Berlin has perhaps been a bit overstated in this story – ‘Heaven And Hell’ and ‘Berlin’, while both interesting, don’t really go anywhere and included covers of Creedence, The Stones and even William Bell, like their own ‘Blow Your House Down’, are perfectly fine, but they point backwards rather than forward. The real tightening up was done – once they had decided to carry on at all - back in Dogtown Dublin. ‘Lady With The Spinning Head (UV1)’ – one, like the slinky ‘Salomé’, of their greatest B-sides - with its guitar riff from ‘Korova 1’ was stripped for parts and used to seed ‘The Fly’ and ‘Ultraviolet’ while further elements from ‘Sick Puppy’ became ‘Mysterious Ways’. ‘Down All The Days’ was shelved but only until it could form the basis of ‘Numb’ on Zooropa, as their red hot – and blue – streak continued.

What the Achtung Baby 30th Anniversary Edition delivers then is not only what is possibly U2’s finest album but also a funky and remarkable history lesson from a time when the biggest band in the world - and other acts attempted a similar reupholstering only to fall on their arses - were foolhardy/brave enough to step back, try on different trousers, and do a brand new dance.