Oh no. Roger Waters isn’t hungry. “I’d like some gravadlax, and that’s all I’d like, thank you,” he says having inspected the Berkeley hotel’s three-course menu, which he then briskly pushes away as if rejecting an autograph request.

The waiter wonders if we’d like an aperitif. “Beer?” I pipe up, having read somewhere that the Pink Floyd founder is an ale drinker. But, no, it turns out he isn’t, not anymore. If he were drinking at lunch, he might have a bottle of lager. But not today; a lime cordial will be fine.

My hopes of a long convivial lunch are dashed. Well, a long lunch anyway. Conviviality has never been a trait widely associated with Waters, writer of brooding songs on the wretchedness of the human condition and perpetrator of rock’s most titanic feud when he fell out with the rest of Pink Floyd in the 1980s. He’s currently restaging The Wall , the Floyd’s Waters-penned, semi-autobiographical concept album about a rock star who feels alienated, goes mad, and becomes a fascist demagogue. Since its release in 1979 the album has sold more than 25 million copies and led to one of the most famous live tours in rock history, involving a 40-foot wall being constructed between the audience and the band—a remarkable exercise in stadium rock theatrics, like Bertolt Brecht with guitar solos.

Our venue is a private room in the Berkeley, a swish Knightsbridge hotel that he favors when he’s visiting London from his New York home. We face each other at a large round table laid out with elaborate formality, alone but for two service staff who periodically ghost through the door. Waters, 67, is tall, dressed in black and has leonine white hair and grey stubble. When one of the waiters lingers, standing behind the rock star in the manner of a footman attending an 18th-century aristocrat, there’s a flash of irascibility.

“If you’re bringing something in, that would be great; otherwise would you mind not standing there, it’s slightly alarming,” Waters says. The hotel employee explains, in a defensive tone, that he’s waiting for us to order from the wine list—”I need to do some service”—before beating a retreat clutching said wine list, leaving a faint tang of resentment hanging in the air.

Waters has a reputation for being overbearing. Nick Mason, Pink Floyd’s drummer, wrote in his autobiography: “Once he sees a confrontation as necessary he is so grimly committed to winning that he throws everything into the fray—and his everything can be pretty scary.” Gerald Scarfe , The Wall’s illustrator, has described Waters (admiringly) as a “megalomaniac.”

His self-belief certainly seems immense. During the meal he has occasion to compare himself with Shakespeare, Woody Guthrie, and Richard Dawkins. Yet there’s another side to Waters, which emerges with a mischievous grin that often sneaks over his features, bringing an amused, lopsided look to his long face. This Waters is relaxed and discursive: convivial, even.

“There’s nothing I like more than lunch,” he says when I remark on his lack of appetite. “Particularly with my beloved. Nothing better than lunch with the beloved; hopefully, sun and a little bit of sea, somewhere foreign. And then sex in the afternoon, perfect.” Out comes the mischievous smile.

Right, I say, wrong-footed by this unexpected insight into Waters’ life with his fourth wife, Laurie. So, um, foodwise, nothing too heavy then for these lunches, no big roasts? “No, I like that too, the English family roast thing. Roast chicken with proper bread sauce is very, very good. I also like big family lunches where it’s hot. I used to spend a lot of time in Greece. That sort of big Greek or Italian family lunch with kids down one end, adults at the other, and it goes on for five or six hours.”

Talk of sex emboldens me to ask about drugs. It was on the Greek isle of Patmos, in the 1960s, that Waters had one of his few LSD experiences. “There was nothing culinary about that trip, as I recall. That was when acid came out of proper laboratories and was beyond powerful. In later years people would talk, not least my kids, about dropping acid and going off and doing things and I’d go, ‘No, that’s not what I’m talking about.’ ” He chuckles. “There was no question of ‘going’ anywhere or ‘doing’ anything. The idea of standing would have been completely wrong. So I stopped all that quite quickly.” There is a gurgle as the waiter, who has crept back in again, pours sparkling water into his glass.

Hallucinogens play a tragic part in the Pink Floyd story. The band formed in 1965 in London, but its core members grew up in Cambridge. Waters’ school friend Syd Barrett was the leader of the group, overseeing their 1967 debut The Piper at the Gates of Dawn . But Barrett’s heavy LSD use triggered a mental breakdown and he was ejected from the band in 1968.

It was widely assumed the leaderless Pink Floyd would fold. Yet Waters, Nick Mason, and keyboardist Richard Wright recruited another Cambridge native, David Gilmour, to replace Barrett on lead guitar and continued to record albums. Progress was haphazard, but they gradually found their feet. Waters identifies 1971’s underappreciated but atmospheric Meddle as the turning point. The most driven member of the band, he was vital in keeping Pink Floyd going after Barrett’s departure and gradually assumed creative control.

During his years as Pink Floyd’s helmsman, from The Dark Side of the Moon in 1973 to The Final Cut in 1983, they became one of the biggest bands in rock history. Barrett may be portrayed as the band’s doomed genius, a psychedelic Icarus, but it was intense, single-minded Roger Waters who made Pink Floyd fly.

Our food arrives. Waters has ordered what must be one of the most expensive pieces of gravadlax in history (£75!) but leaves his exorbitant slice of fish untouched as he talks about The Wall’s return. He is on the European leg of a tour that began in North America last year, where it was one of 2010’s highest-grossing concert tours, taking more than $89 million. “It has been incredible; it couldn’t have been more successful,” he says. The album, which was also made into a film starring Bob Geldof, tells the story of Pink, loosely based on Waters himself. Pink’s father dies in the Second World War, as did Waters’ father Eric. Pink’s marriage collapses, like Waters’ turbulent first marriage to the potter Judy Trim did in 1975. Pink’s breakdown into isolation and self-loathing as a result of rock stardom mirrors Waters’ experiences. It was inspired by his disillusionment playing huge stadium shows with Pink Floyd, climaxing in a notorious occasion in Montreal in 1977 when he spat at a disruptive fan.

It must be odd, I suggest as Waters cuts into his gravadlax, to revisit an album made under such emotionally oppressive circumstances. The personal aspects have faded, he says: “I’m happy to be an actor in a historical document.” He loves singing the profoundly pessimistic couplet “Day after day, love turns grey/ Like the skin of a dying man,” from “One of My Turns,” a song inspired by the breakup of his marriage. “I love it,” he reiterates, forking salmon into his mouth. My fork pauses over my suddenly less attractive grey-fleshed halibut.

The Wall is also haunted by his father’s death in the battle of Anzio in Italy in 1944, when Waters was just a few months old. The theme of war is prominent in the new staging. Audiences are encouraged to send in photos of loved ones who have died in conflicts, which are projected during the show. In the United States, Waters invited wounded veterans to join him backstage during the interval. The staging caused controversy last year when the Anti-Defamation League, a pro-Israel pressure group, took exception to another aspect of the show. “They read something in Rolling Stone about the Star of David being juxtaposed against a dollar sign and said this was bringing out the worst racial stereotype of the grasping Jew. They were sort of accusing me of being Shakespeare, I suppose, which is fine.” He chuckles. It takes me a moment to realize he means The Merchant of Venice .

Brought up in a socialist household by his teacher mother, Mary, Waters is more outspoken than the average rock grandee. “Power resides in ideas,” he says. What sort of ideas, I ask, growing accustomed to my role as Boswell to his Johnson. “Economists are important. So are radical free thinkers in theology.” Like who? “Richard Dawkins is the name that springs to mind, he’s about the most radical. I myself am a radical atheist and I propound my views from time to time, when I suggest that it is not God’s will that you become a Muslim, it’s an accident of birth, it’s geography.”

Can rock music change the world? “Insofar as it ever was able to, it still can. I would like to think I am no less effective than Woody Guthrie was. I may be overblowing my claims.”

Our plates are cleared away and coffee ordered: white with sugar for Waters.

The Wall marked the beginning of the end for Pink Floyd’s classic line-up. Waters’ bandmates chafed at being bossed about, and they ruptured after 1983’s The Final Cut. A vicious falling-out ensued as Waters unsuccessfully tried to prevent Gilmour, Mason, and Wright from operating as Pink Floyd.

However, in 2005 the band reunited at the Live 8 charity concert, and relations appear to have thawed. With Wright’s death in 2008, there are only three of them left. “Nick [Mason] and I have become close friends again, which is great. He was always my friend in Pink Floyd. So the fact we fell apart and lost contact for many years was a shame.” He is more guarded about Gilmour but things have improved enough for the guitarist to play a cameo on “Comfortably Numb” at a forthcoming Wall concert. “Yeah. So he says. That’ll be great. I look forward to that,” Waters says in a measured way, stirring his coffee.

Has he become less controlling as he has got older? “No,” he says emphatically. “No. That’s the way the work got done. I am the director. I always was. It’s like you don’t say Scorsese is such a controlling character, or Bertolucci or whoever it may be—you go, ‘Oh, didn’t they make good movies.’ And they do it because they’re controlling. Sometimes it becomes problematic if you have a thing called a ‘group’ and one person is controlling it because he’s doing all the work.

“So, no, I haven’t become less controlling. I’m much happier now because I’m not pretending to work in a group. That’s not to say I don’t work with a group of people.” He reels off a list of names of people working on the Wall tour. “We’re a real close-knit team, we’re like a family, it’s fantastic. What I haven’t got is, like, somebody who thinks [he adopts a gormless voice], ‘I’m in the band too, why is he telling me what to do?’ Just because he knows more than you do and he’s the writer and it’s his thing, that’s the way it is.”

Waters has released four solo albums since leaving Pink Floyd. None has come close to matching Floyd’s success, though he says 1992’s magnificently ambitious Amused to Death is “one of the things I’m proudest of in my life.” Was there a chemistry in the band that he hasn’t managed to repeat? “It was great, yeah. That was extremely lucky for all of us and we made some fantastic work together.” He takes a sip of coffee. “I have to say, and this might just be an opinion and I might be wrong—no, I probably shouldn’t say this.” Please feel free to, I say.

“All right, I will. The work I’ve done since I left the Floyd is all way more successful than the work they’ve done since they left the Floyd. That’s just a personal opinion. They may have sold more, I’m not sure what the figures are.”

Though he can’t resist the jab, Waters strikes me as far less prickly than either the Floyd’s turbulent history or The Wall’s tortured subject matter might suggest. Despite the relative lack of food, our lunch has unfolded at a leisurely rate. As our coffee cups are removed, and I divert the eye-watering bill from his room charge to my debit card, he talks about the time a scheduling quirk left him playing a solo tour in the United States at the same time as his erstwhile Pink Floyd bandmates. It was 1987. He was playing middling-sized venues holding about 1,500. Meanwhile the Waters-less Pink Floyd was popping up like bad memories at all the same cities playing huge stadiums holding many tens of thousands. “That,” he says, mischievous smile reappearing, “was character-forming.”