In the days following the terrorist attacks on New York, the Pentagon and Pittsburgh on September 11, 2001, Radiohead were not the band I wanted to listen to. As news networks broadcast raw hand-held footage shot by bystanders – film that probably cost a couple of dollars to process but looked like scenes out of Independence Day – and as surrealist montage and reportage fused into one, I had to force myself to play their last three albums. Too emotional. Too paranoid. Too aware. Thom Yorke, a singer plagued by "unborn chikken voices", the Chicken Licken of rock ‘n’ roll in fact, might’ve wondered if it wasn’t an acorn that hit him on the head but a piece of the sky, a chunk of American Airlines Flight 11 from Boston, slicing through a stitch in time.

As far back as OK Computer you could find eerie pre-echoes in songs like ‘Airbag’ ("In the next world war/In a jackknifed juggernaut/I am born again"), which might’ve been written by Jeff Bridges’ character in Fearless, a guy who walks away untouched from an air accident with delusions of immortality. In ‘Idioteque’ off Kid A, stray lines escape the cold Kubrick surfaces of the music like interplanetary SOS signals:

"Ice age comin’, ice age comin’’… We’re not scare mongering… This is really happening…

Your reporter didn’t want to be catching a train to Belfast; he wanted to be under the table in the nearest tavern. If the purpose of terrorism is to inflict terror, then I didn’t want to give the perpetrators the pleasure. I wanted to be frivolous. I wanted to forget.

But Radiohead wouldn’t let me.

When the world goes to war, the weird turn pro. Throughout the last century, creative minds of every discipline have attempted to make sense of war by making war on sense. The responses to the social traumas of the times – not just international conflict but industrial revolution, racial tension, technological convulsions – took the form of a whole prism of isms: cubism, surrealism, dadaism, modernism, post modernism, abstract expressionism, vorticism.

After World War I, representational art couldn’t hack it as a means of conveying The Horror. Strapping young boys went into battle and came back in cubist bits and pieces. TS Eliot’s ‘The Wasteland’ was one of the first of the strange new 20th century visions, a panorama of echoes with its texts edited – or rather, cut up – by the father of modernism Ezra Pound. Joyce and Beckett followed. Sergei Eisenstein’s Battleship Potemkin found its image in Francis Bacon. Fritz Lang’s Metropolis, Charlie Chaplin’s Modern Times and Lorca’s Poet In New York dwelled on the dehumanising forces at work in urban societies.

Schoenberg and Stravinsky punched holes in classical music for Stockhausen, Cage and Reilly to peer through, and even folk tunes like ‘I Wish I Was A Mole In The Ground’, a strange ditty recorded by Bascom Lamar Lunsford in the late 1920s, corresponded with Breton and Bunuel’s Surrealist manifestos. A decade later milestones such as Picasso’s ‘Guernica’ and Dali’s ‘Autumn Cannibalism’ refracted the ravages of the Spanish Civil War. After bearing witness to the slaughter of innocents, neither painter could ever see the human form in the same way again. Similarly, in 1939, Billie Holiday recorded Abel Meeropal’s, ‘Strange Fruit’, written about lynchings in the deep south, a song full of strange and grotesque images of bodies hanging like fruit for the crows to pluck and the wind to suck.

Rock ‘n’ roll itself was born in the shadow of the bomb: that crazy cowboy riding the missile in Dr Strangelove could’ve been Sam Philips or Jack Clement. Ginsberg, Kerouac, Burroughs, Pollock and Charlie Parker tried to expel through their work the dread that entered the species’ nervous system at Hiroshima-Nagasaki, 1945. 30 years after the Second World War, Captain Beefheart’s ‘Dachau Blues’ from Trout Mask Replica attempted to translate the unspeakable truths of the death camps – the "Bluebeard’s castles of our century" in the words of critic George Steiner – through dada blues and spasmodic jazz.

The 1960s brought their own shitstorms. Bob Dylan wrote ‘A Hard Rain’s A Gonna Fall’ in ’63 as a spooked response to the Cuban Missile Crisis. At Woodstock 1969, the height of the Vietnam War, Jimi Hendrix made a napalm painting out of the ‘Star Spangled Banner’. Neil Young reprised this act with Crazy Horse in 1991, taking Sonic Youth on tour during the Gulf War and saturating songs like ‘Blowin’ In The Wind’, ‘Powderfinger’ and ‘Cortez The Killer’ with white-hot hails of feedback. U2 hauled their Zoo TV extravaganza across America soon after, parodying the madness of a conflict that for many seemed to exist only in the hysterical nightmare mind of CNN.

In the last years of the century, Radiohead perfected their own form of comic-paranoiac expressionism, a sound that encapsulated, in the word of one Q writer, "what it’s like to feel terrified by the times".

And in September 2001, in the wake of those attacks on a no longer impregnable Fortress America, Radiohead were the last band you’d want to see live, but maybe the one that mattered most. The night of the 11th, they were on stage in Berlin, Thom Yorke dedicating ‘You And Whose Army’ to US President George Bush.

As the world entered a period of queasiness on a par with the Bay Of Pigs, the band journeyed on to Belfast, opening that show with ‘The National Anthem’ and sounding like – well, there’s no other metaphor for it – a war machine being cranked into life. The pre-show tape selection of crooned ballads and doo-wop tunes only added to the eerie 1930s atmosphere. Over two hours and ten minutes Radiohead played a taut set, with songs like ‘Morning Bell, ‘Paranoid Android’, ‘Pyramid Song’ and ‘Exit Music (For A Film)’ all taking on chilling new meanings, until eventually the tension dissipated into ‘How To Disappear Completely’ and everyone left the building feeling no better but perhaps a little less alone.

Anybody want a drink before the war? Champagne in a plastic tumbler, in a too-bright room. It’s an hour or so after that show in Belfast’s Odyssey Arena, and I’ve just been asking Radiohead guitarist Jonny Greenwood if there’d been any talk of how to approach the night’s set in the light – or darkness – of the week’s events.

"No, none at all," he says. "I think everyone in the room had gone through the same week. You lose the will to be upbeat, obviously."

Was he tuned into the resonances in songs like ‘Airbag’ and ‘Idioteque’ on stage?

"Yeah, obviously, but that happens all the time I suppose, resonances with what’s going on. Although let’s face it, the last week was the biggest event of the century."

He’s picking listlessly at the subject rather than getting his teeth into it. I take it to be the infamous Radiohead reticence, or a guitarist’s prerogative. Only later do I hear that his wife can’t get a flight out of Israel.

As Jonny’s bassist brother Colin enters the room, I’m talking about how the Kid A and Amnesiac albums reminded me of the consparanoia TV shows that prevailed from the late 70s to the mid-80s, as unease in the Middle East infected another generation of post-bomb babies. I’m thinking of Quatermass, Edge Of Darkness…

"Threads," remembers Colin, referring to the documentary style projection of a nuclear winter that put the fear of God into every schoolchild old enough to understand its implications.

Jonny: "I remember going into primary school and everyone saying, ‘There’s going to be a nuclear war today’."

"The paranoia," continues Colin. "And Day Of The Triffids. It’s weird playing these shows at the moment. You play some of the songs and it just feels too much. But playing Berlin was really good two nights ago, Tuesday night. 11,000 people had bought tickets and they all came and there were like forty walk-ups."

Earlier, as Thom jerked like a wired-up rag doll to his band’s relentless motorik during ‘Idioteque’, singing, "Women and children first" in a shrill, panicked voice, I kept thinking of Martin Amis’s nuclear war essays, written under the influence of terrified new fatherhood in the mid-80s. Some men find in the role of parent new survival mechanisms, reasons to be cheerful parts one, two and three. Others become susceptible to all manner of survival phobias. A week after the Twin Towers, Amis was reprising those essays in a Guardian feature entitled ‘The First Circle Of Hell’. "The illusion is this," he wrote. "Mothers and fathers need to feel that they can protect their children. They can’t, of course, and never could, but they need to feel that they can. What once seemed more or less impossible – their protection – now seems obviously and palpably inconceivable. So from now on we will have to get by without that need to feel."

Thom Yorke became a father some months ago – one wonders how it affected him?

"I think with him it’s definitely the former rather than the latter," Colin says. "It’s really interesting, ’cos it’s obviously been so good for him as an experience. I think now with Noah he definitely has that pragmatism of having a child and that’s what’s important. I was talking to him about it in Berlin. If you’re not gonna be with your kid then you might as well make sure it’s worthwhile being away. And that’s been great, I think. He’s been less obsessing about the potential perils of the future and more thinking about making the moment worth it and making time matter. It’s fucking great, ’cos all you wanna do is see everyone happy that you’ve been working with for 15 years. And you can see with Thom and Phil, they’re really enjoying making this work because they want to be home as well."

Jonny: "I think it makes you aware of what’s important about making music and what’s not worth wasting – all that pain and the unproductive side gets avoided."

Flashback to another moment from the Belfast show: the refrain of ‘You And Whose Army’ struck a chord with the crowd for obvious reasons, but was offset by the rather amusing premise of Yorke inviting "the holy Roman empire" outside for a scrap. On the night, it sounds like a guy arguing both ends of the sectarian divide in one song.

"It’s a good example of what I love about his lyrics," observes Colin, "that combination of direct involvement and aggro and that sublimation at the end of it, taking it somewhere else and elevating it at the end. That’s a mark of his great gift as a songwriter, to make you feel things viscerally and transport you from that point to somewhere else."

Of course, the inverse of that is ‘Exit Music (For A Film)’, the tale of two lovers fleeing from peril, ending with the softly sung lines, "We hope that you choke".

"That’s true," Colin concedes, "his voice always jars for me at the end, when he’s singing that, and people are singing along with it as well, but in a good way, it’s a good dissonance."

One thing about Radiohead in 2001 – they’ve become almost an amorphous organism. Anyone who saw the grim documentary Meeting People Is Easy will understand exactly why the musicians and Yorke in particular have grown so wary of the kind of Best Band In The World hoopla that accumulated around them between The Bends and OK Computer.

These days, they infiltrate the culture in more insidious ways. In an interview last year, Brad Pitt compared them to Beckett. There’s a veiled reference to ‘Exit Music (For A Film)’ early in Chuck Palahniuk’s novel Choke. Neil Jordan wanted to use their music in In Dreams but couldn’t because he feared the sounds would overpower the visuals.

Strange bedfellows until you consider the inevitable connections between the work of all concerned and recent events. Pitt starred in the film of Palahniuk’s Fight Club, whose premise centred on the notion of domestic lo-tech terrorism. Palahniuk’s novel Survivor is a tale narrated into the black box recorder of a crashing plane by Tender Branson, the last living member of the Creedish Death Cult. Neil Jordan, for his part, explored the doomsday atmospheres of the Cuban Missile Crisis in his adaptation of Pat McCabe’s The Butcher Boy.

Mind you, all this is news to Jonny Greenwood – he still has trouble getting his head around hearing Radiohead’s music disseminated through mass media.

"You see it on trailers for television shows, from football to documentaries about Concorde," he marvels. "It’s strange how it seeps through and doesn’t get heard that often in other ways. The first time you hear your music on the radio, it’s really weird that it’s coming out of a box where nothing’s moving. I still can’t get over the shock of it. And most times people don’t know that it’s Radiohead in a way."

The Radiohead on stage tonight are the end product of a process of deconstruction that began shortly after the OK Computer campaign. When the quintet reconvened to record a follow up to that album in Paris and Copenhagen at the start of 1999, they were a band of blind men holding different parts of the elephant. Yorke, the group’s benevolent dictator (he once likened Radiohead to the UN, with himself as America), seemed to be fighting shy of melody, choruses, even lyric. Under the influence of Krautrock and the Warp back catalogue, his strategies were radical to the point of advocating that the players abandon their chosen instruments. Guitarist Ed O’ Brien on the other hand, figured they should record an album of straight ahead three-minute tunes. Jonny Greenwood didn’t necessarily agree with either, being in thrall to composers like Olivier Messiaen – one of the pioneers of the ondes martenot, an instrument that would feature largely on the new sounds alongside a whole battery of black boxes and analogue synthesizers – and Charles Mingus.

Jonny: "The Mingus thing started with the excitement of discovering those big band records that weren’t how big bands are normally perceived. Suddenly there’s this chaotic dark, really vicious music. But then we had to obviously hire in a brass section and try and get them to play like that, and me and Thom were in the room trying to conduct, and there’s not many gestures you can do! But they were amazing, and really young as well."

The Kid A sessions were strained affairs as the band groped to find common reference points. There were echoes of U2’s Achtung Baby and REM’s Monster traumas: different configurations of personnel fighting to reconcile melody with experimentalism.

"It’s also the relationship between all the people involved as well," Colin reflects. "It’s like a mid-life crisis, whether you still like each other, or are you happy making compromises and stuff like that. We were trying to find another way of doing what we do without ending up in a similar sort of space as OK Computer, where there was this feeling that you were being fast-tracked into being processed as the next REM or U2 type thing. I’m not slagging them off, but in terms of how they’re perceived by people. But I think it was also just a fear of putting a record into a shop. I think we had to definitely rethink a lot of things. They were studio albums as well, which was the first time we’d done that in a way, because before we’d always recorded music we’d played live, like OK Computer and The Bends."

When Kid A was released in October 2000, its abandoning of guitar-based song structures was received with some incomprehension by not just the band’s critics, but many of their peers. The album got guardedly positive reviews, but one often suspected this was because the writers were too chickenshit to admit they didn’t get it. In retrospect, Kid A was as misunderstood as OK Computer was overrated. It wasn’t even that much of a departure, especially if you figured the intervening Airbag/How Am I Driving? extended EP into the equation.

"It’s very interesting, that whole diffusing a sticky situation," Colin says. "Nick Hornby wrote that thing in the New Yorker where he thought we were terrible because we’d sort of betrayed the faith that people had after The Bends, that sort of nostalgic way of writing. But I think that record is really fantastic, and Amnesiac is more a sort of echo of what we’d done with Kid A. It was a fine line of wanting to do something that was creative and also wanting to try and back away from all the media nonsense. And I think it’s a sideways thing; looking back on it Kid A was really strong, it wasn’t just avoiding people who wanted us to do another OK Computer."

I put it to Jonny that a lot of the Kid A criticism was like football commentary, as in "They’re not fielding their best players" or "They’re not playing to their strengths: Thom’s tunes and Jonny’s guitar".

"It’s as though lots of people who really liked us heard a few bands coming out who sounded similar," he considers, "and they were thinking, ‘Oh, Radiohead are going to show us how to do it!’ They wanted us to sound like the bands who sound like us, but better!"

"It was spurned lover stuff," adds Colin. "I think it was a real fight in the studio as well. There was that conflict between wanting to do something that was good, but also wanting to do something that was unexpected. That was the big tension. You have to deal with the concept that you have to put a record out into the public arena, and if you read the papers you’re obviously aware of where other people want you to go. And if that’s not where Thom is comfortable, it causes a lot of tension and it can impact upon the creativity as well. You feel that the tools you have to do your music have been taken away from you and sort of appropriated and debased."

Jonny: ‘I remember a version of ‘Motion Picture Soundtrack’ that we recorded that had the kick and the snare, and it just had no magic to it, and the other version was far better. The point is, we played both versions to our managers and they said, ‘Yeah, it’s better but it’s not going to sell as much!’"

Of course, the version without the backbeat made the final cut. But interestingly enough, American audiences, long ridiculed for their conservatism, welcomed Kid A and its sister album Amnesiac with open arms.

"We’ve had the most support in the world from America on the last two records," Colin says. " And this last touring that we’ve done in America, playing those open air concerts, the references we always like to make are bands like The Grateful Dead, some concerts like Phish did, Neil Young I guess, a sort of roaming festival, open air, recording bootlegs vibe. And it was really privileged to be able to play open air in Chicago or in Seattle or Liberty Park right next to the Trade Towers for two nights; it was the most beautiful setting. What we mean in America is completely different to anywhere else in the world. You can lose a lot of baggage halfway across the Atlantic, and you can go to America and take them on their terms, not English press terms. And we’ve definitely relished that."

So what next for Radiohead? Contrary as ever, they seem freed up and optimistic in a world that feels anything but. The forthcoming I Might Be Wrong mini-album will showcase the band’s robust live arrangements of material from the last two albums. After that, Colin talks about a return to premiering new songs live before re-entering the studio.

"I think we’re in a very similar situation now as we were going into OK Computer," he suggests. "I think we had to do two records and take time out to get back to that point, ’cos definitely by the end of touring OK Computer you felt you were being propelled. And because a lot of the structures on Kid A and Amnesiac were a lot looser, you have to improvise and make up things a tiny bit, so there’s more room for random accidents. Whereas with OK Computer we’d honed it to this stadium fulfilling thing, every song had the same thing played every night and it stopped being musical and became more about repetition and less about performance.

"It’s very interesting, the body language of people on stage. (With Thom) it’s all from his body. His dad was a boxer and he taught Thom how to do some boxing when he was a kid and you can see that sort of physical, brawling, punching quality. He’s got such amazing rhythmic intuitive drive."

After the show, Thom’s not doing press but he is hanging out in hospitality. Wearing a scrub of beard, he looks, as ever, like a man on leave from The Carters’ country noir classic ‘Worried Man Blues’, the story of a guy who lays down to sleep by a river and wakes up in chains.

A couple of hours earlier he’d dedicated ‘Street Spirit’ to "all the Americans who can’t get home", and I was reminded of what it must have felt like watching Neil and Crazy Horse on that Gulf War campaign. Elsewhere in the show, scouting for a line that might make sense amidst images of a traumatised fireman breaking off from digging in the Manhattan ruins to speak to a priest, or of exhausted medics cutting themselves and putting salt on the wounds to stay awake, the refrain from ‘Lucky’ seemed to hang in the air long after it was uttered.

"Pull me out of the air crash… we are standing on the edge."