I’m asking Roger Waters a question about his new film – the fourth and most successful attempt to bring Pink Floyd’s 1979 concept album The Wall to the big screen – when he suddenly interrupts me. “You know why I don’t read the Grauniad any more?” he asks, narrowing his eyes. I’m afraid I don’t. “I’ll tell you why. When I did The Wall in Berlin in 1990” – a record-breaking charity performance – “they printed a big picture, half a page, no article, and underneath it said something like ‘Last night, Pink Floyd played their record The Wall in Berlin and the sound was terrible.’ Full stop. And I thought, ‘Fuck you, that paper is never coming through my letterbox again.’”

This is, of course, precisely the kind of thing Roger Waters is supposed to do in interviews. Always the most uncomfortable of rock stars – it is hard to think of anyone who made heavier weather of being a vastly successful musician than Waters did once Pink Floyd went stratospheric in the 1970s – he is also, legend has it, far more prickly and defensive than you might expect someone who’s sold more than 250m albums to be. He is ever watchful for a slight, real or imagined, such as suggesting that he wasn’t the band’s main creative genius after the departure of the late Syd Barrett in 1968, or that his subsequent solo career may have failed to match that of his former bandmates. Indeed, before I meet him, I receive what I think is a tacit warning from his publicist about one line of questioning. It takes the form of a story about a foreign journalist who attempted to kick off a recent interview with the words: “A friend of mine wanted to ask you if Pink Floyd would be re-forming.” Waters is reputed to have responded: “Tell your friend to fuck off.”

But his ongoing disappointment at the Guardian’s 25-year-old picture caption notwithstanding, Waters at 72 positively radiates health and contentment. On his website, amid stuff about his support for the pro-Palestine Boycott, Divestment and Sanctions Movement, you can find video of Roger Waters cheerfully taking part in a TV cookery show, a state of affairs that would once have seemed no more likely than Roger Waters being appointed archbishop of Canterbury. “Well, over the years, I’ve come to realise how lucky I am that people like what I’ve done and are happy when I walk into the room and start playing my songs,” he says. “It never really dawned on me until, I think, 1999. Don Henley asked me to do a charity gig in Los Angeles. It’s about 6,000 people, and I walked up and felt this whoosh of what you could only describe as love from the audience. I thought, ‘Fuck me, this isn’t bad!’”

Hang on, you realised that you enjoyed playing live almost 35 years into your career? “I’m serious! I think that was the great turning point. I thought, you know what? Maybe I’ll go back on the road. I like this. There’s something great about it.”

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It is a point underlined by the new film, which matches footage of Waters visiting a memorial to his father, who was killed in action in Italy in 1944, with film from his 2010-2013 world tour, the all-time highest grossing by a solo artist. For all the emotional impact of what Waters describes as “the road trip”, it is the live stuff that’s striking. There shouldn’t be anything odd about seeing a rock star enjoying performing an arena show, except for the fact that, well, Waters is performing The Wall, an hour and a half of music inspired by, and frequently about, how ghastly it is playing arena rock shows. “I’ve become confident, a lot more confident, and lot more comfortable on stage.” He thinks it might have something to do with an occasion some years back, when he was asked to speak to pupils at his son Harry’s school. “The most terrifying thing I ever did. The idea of standing in front of 80 10-year-olds was absolutely terrifying. I’m serious. Couldn’t sleep for weeks. I couldn’t think what I was going to do. It was really weird, I couldn’t work out why I was so scared. So that’s something I had to confront. And I’ve transcended it in some way. I don’t know what’s happened, but something internal has happened.”

Facebook Twitter Pinterest Roger Waters on tour in 2011.

For all his sunny disposition, you still occasionally get a hint of the man who wrote the lyrics for Pink Floyd’s Animals, one of the most rancorous albums of the 70s. At one point, an innocuous question about the state of the music business ends with him embarking on an extended rant about the tax arrangements of Apple – “Why do we give a shit about society? Why should we pay taxes? Bollocks to you!” One report claimed he’d relocated to the US in protest at the 2004 hunting ban. He frowns when I mention it. “Of course not. That’s not quite how it was.” He pauses. “Well, it may well have been that in some interview or other I might have been so strongly pro the people of the British countryside … I went to Hyde Park and joined 100,000 of them who had marched from all over England to protest about the anti-hunting bill, and I felt very strongly that it was a terrible piece of legislation.”

He doesn’t want to talk about this, he says, but he can’t seem to stop himself, and off he goes: the ensuing monologue takes in “MPs who’ve never been to the countryside”, a passage from Rudyard Kipling’s Stalky & Co, and the difference between hunting a fox and snaring animals for fur. “You know what people should do, if they’re really concerned about wild animals, is to stop people from owning cats,” he says. “They kill 35m songbirds a year. I mean, I’m not saying they should, but this particular hobbyhorse about foxes …” His voice tails off. “Anyway,” he says, “I don’t mean to go on.”

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He’s making a new solo album, his first since Amused to Death in 1992. Like The Final Cut, it is another concept album about war, but as Waters points out, he’s been writing about that particular topic since 1968. “One of the first songs I wrote was Corporal Clegg,” he says. “I’ve always been shackled to that sort of socialist, humanitarian idea that there must be a better way of doing this. We need to start chipping away at the idea that somehow socialism lost and capitalism won, and the free market is the answer to everything and everything will work itself out and everybody will live happily ever after. No, it won’t. That’s not going to work.”

He says one of his demos for the forthcoming album contains a caveat, that may or may not make it to the finished version: “There’s a bit in it where it goes, ‘If you’re one of these people who says, ‘Roger, I love Pink Floyd, but I can’t stand your fucking politics …’” He pauses and laughs. “‘You might as well fuck off to the bar now.’”

With that, our time is up. But just before he goes, the topic of the Grauniad’s response to his 1990 Wall concert rears its head again. “I’ll tell you what I’d like you to do: check the archive,” he says. “If I’m wrong let me know. Sometimes I get things completely wrong. And I’m always happy …” He corrects himself: “Not happy, but very prepared to be wrong about everything.”