Amid all this wreckage, only Young’s career has consistently hit the heights of artistic excellence or matched the impact of those early years. The tension may have been as destructive as it was creative, and it was Young’s single-mindedness that tore at the fabric of Buffalo Springfield and CSNY, but it’s also the quality that makes his work vital. “I don’t think he ever thinks about other people’s expectations,” says LA Johnson. “He does it all for himself. It’s about the creativity. It’s about doing all the things that he wants to do, and getting them done and enjoying the process. He’s a worker.”

In which case, it may not be coincidental that the outbreak of peace in CSNY coincides with the acceptance, by CS&N, of the pre-eminence of Y.

“Neil and I get on fine these days,” says Stills. “David and Graham and I occasionally have the occasional old married people shit. Sometimes we lose our sense of humour and that’s deadly.”

“I don’t think we’ve ever liked each other as much as we do now,” says Nash. “When you get a little older, you begin to realise the things that annoyed you about these people years ago were meaningless. OK, so he wants to play it in a different key, so what? Why argue and why shout and scream, and why do all the shit that we did?”

The old antipathies were “stupid things, fuelled by drugs,” Nash says. “Stephen asking me to sing a minor vocal melody through a set of major chords, and my body wouldn’t do it, ’cos to me it was wrong, just awful-sounding, and he kept trying to force me to do this thing, and I finally threw him out of my house and didn’t speak to him for two years.

“It’s just the way it is. It’s craziness. Young people growing up with fame and money and power and position, and blowing it.”

Mike Cerre [see panel, left] – who usually reports on real wars, but who found himself “embedded” on the Freedom Of Speech tour – bore witness to an extraordinary moment of unity, prior to a 2006 show in Washington DC. The previous night, CSNY had played Atlanta. The conservative crowd, offended that the band was leading a chorus of “let’s impeach the president” at a time when troops were in mortal danger, had responded with catcalls, one-fingered salutes,
and a partial walkout. The musicians weren’t able to fully appreciate the anger of the Atlanta audience, but they were aware that something was happening.

“We knew the hostility was there because we could see the bomb-sniffing dogs,” Young says. “When I came back to my hotel at night after the show there would be guards on my room, and when I went in people would go and check behind all the curtains. We chose not to film that part of it, because I just don’t want to make that something people think about all the time.”

Didn’t he thrive on that kind of antagonism?

“No,” he says bluntly. “The film thrives on antagonism, but for me, that was the most hair-raising, nerve-wracking, terrible experience. I don’t want to do another tour like that! I’d rather be playing with The Rolling Stones.”

“Neil was very concerned with the death threats,” Cerre says, “and that’s why his family wasn’t out on tour with him. Before the Washington show, it was like a basketball team gathering before going out on the court. Neil was almost in tears, and he said: ‘Guys, I really feel emotional tonight. I just want you to know, I couldn’t have done this without you, and I’m so thankful we’re all here together to do this.’ And they all went around and were just kinda bucking each other up. And I imagine that’s what it was like when they were all launching their careers and didn’t know where this thing was going.”

Musically, things aren’t quite so harmonious. Early in CSNY: Déjà Vu, snatches of Crosby’s “What Are Their Names” and Nash’s “Military Madness” serve to underline the suspicion that CSNY were a group of their time, and that time was the pre-punk era. But something sparks when they play the Buffalo Springfield’s “For What It’s Worth”. Yes, the vitality has drained from Stephen Stills’ voice, but the intrigue of the song remains, and it fits the War On Terror as neatly as it did Vietnam.

“I’ve been singing that song a long time,” Stills says philosophically, “and it seems lost. I was so young when I wrote that, and it was that visceral instinct. I didn’t think about it. And I keep trying to get back there.

“That’s also the first music in the film,” he goes on. “At the screening at the Sundance Film Festival, I was going, ‘Get on with it.’ And then we finally did, and that was the first cheer from the audience. But there’s also the fact that I sang the piss out of it, and Neil and I shredded the end of it. We had a nifty ending that we’d never quite made before. We shredded it.”

Stills prefers to make light of the tour’s politics, even though he continues to support Democratic campaigns offstage. “We played for two bloody hours. I thought it was great and cathartic because we got all the dated, boring-assed fucking protest music out of our systems. After that it was like, ‘Great, now can I play some blues, please?’ With all respect to Neil, I’m not critiquing as much as saying what I felt. Although I guess I’m taking my life in my hands admitting everything to a British journalist.”

This, remember, is what they sound like when they’re getting on. But Mike Cerre believes the spirit of fraternity is genuine and heartfelt.

“Neil was leading the way, and they bought into it and were as glad that it happened as anybody else. David sums it up towards the end of the film, when he says, ‘It got to the point where we believed in ourselves again.’ That was a legitimate expression of how much this was changing them.”