The entertainment business is a world of smoke and mirrors, in which nothing is ever really as it seems. Take the notion of success: these days, we are constantly told how the music industry is being “saved” by Adele, as if her success somehow trickles down through the entire structure.

But though she’s clearly the most successful recording artist of the last few years, she’s by no means the most successful solo performer. How could she be, when she never seems to perform? So: who is the most successful solo performer on the planet?

It’s the chap sitting opposite me in this five-star London hotel, a grizzled veteran of 72 years who has parlayed youthful psychedelic experimentation and personal anxiety into a multi-million-dollar industry of his own.

Roger Waters knows a thing or two about smoke and mirrors, having staged the highest-grossing solo concert tour of all time – if one’s idea of “solo” can accommodate a 12-piece band and crew numbering hundreds. The Wall, the concept album he wrote for his old band Pink Floyd, was transformed into possibly the most elaborate spectacle ever presented on stage from 2010 to 2013, the latter-day equivalent of producing a Wagnerian opera, then packing it up and taking it around the globe for years.

It’s an extraordinary experience, even if, like me, you’re lukewarm about the Floyd. Musically, its bombast seems to come from another age (which, originating in 1979, I suppose it does), but the staging, with state-of-the-art animations projected onto the wall itself, and a full-scale WW2 fighter plane dive-bombing across the arena at one point, is just extraordinary.

For once, you can see where every last cent of your ticket dollar has gone; but it’s the kind of huge show that only makes commercial sense with economies of scale, requiring that the spectacle be performed hundreds of times to earn back the development costs.

And boy, has it ever earned back. Each performance of The Wall grosses around $2m (£1.3m) – at a few venues, almost double that – so the entire tour has grossed somewhere in the region of $460m, from over four million ticket sales. Close to half a billion dollars. Not bad going for a former architecture student with a bass guitar and a penchant for introspective angst.

“We were 179 people on tour, all day, every day,” explains Waters. “There were 60 18-wheeler trucks, so there were 60 drivers, alone! It was a huge crew – only 12 in the band, but a big, big crew. And what a huge privilege it was to be part of that family for three years, because they were lovely. It’s what it must be like to be circus people.”

The overheads, accordingly, were just as spectacular as the show itself. Even hardened stadium-rock veterans were staggered by the logistical demands it made.

“I remember when [The Eagles’] Don Henley, an old friend of mine, came to see the show,” says Waters. “Afterwards he came backstage, walked into my dressing room, sat down and went: ‘Wow… How do you make any money?’ I said: Don’t worry, I’ll be alright. I can feed the cat!”

Even now, the show remains a solid earner for Waters – the latest offshoot being the DVD Roger Waters The Wall, which presents an entire performance, punctuated with inserts of the auteur driving his Bentley to war graves across Europe, taking out his trumpet and playing “Outside the Wall”, the work’s closing song. It’s a neat piece of misdirection which, while seeking to pay tribute, avoids military connotations.

For Waters, it’s a personal tribute not just to his father, who died in the Second World War, before Waters ever got to know him, but also to his grandfather, who likewise died in the First World War before Waters’s father got to know him: one has to wonder what kind of cumulative effect two generations of fatherless upbringing has wrought on the singer. It’s certainly furnished him with the enduring creative mainspring for his art, as a recurrent motif in several projects, including an entire album, The Final Cut, about what he considers the betrayal of fallen British servicemen through successive conflicts.

But, aged 72, oughtn’t he to have reached some kind of closure by now over his father’s death? By way of an answer, he tells me about a new friend he’s made, called Harry Schindler.

Jack Waters, director/musician Roger Waters and musician Harry Waters attend the "Roger Waters The Wall" premiere during the 2014 Toronto International Film Festival (Getty Images)

“Harry’s a lovely fellow, from Bethnal Green, lives in Italy now,” says Waters. “He saw me on television, when I visited the Commonwealth War Graves Commission in Cassino. He had no idea who I was – he said, ‘I never heard of The Pink Floyds, you know – I stopped at The Beatles’! He said, ‘I thought, this chap needs a little closure, and funnily enough, I was in the Sherwood Foresters, fighting about a mile-and-a-half away on the day that this chap’s father was killed’ – and, bugger me, if he didn’t find out exactly where!

“And then he went to Aprilia, the town nearest to where my father died, and persuaded the town council to build a memorial, in the playground of some elementary school in Aprilia! So, on 18 February 2014, I went over, and we had a big unveiling in this schoolyard, 70 years to the day after my father was killed. So you’ll have to excuse me if I get a bit emotional.”

And, indeed, the flinty countenance of this rock star, known for his ruthless streak, is starting to crumple as, on the verge of tears, he recalls this selfless act of humanity by an old veteran who simply wanted to lessen someone’s burden a little. “Harry’s a good man,” he concludes. “I’m taking him to lunch tomorrow. He’s 94 now.”

The theme of remembrance played a significant part in the Wall show, with one particularly moving visual sequence featuring a series of hundreds of photographs of the fallen accompanied by brief details which suggest the nature of their passing – a child from Iraq; a New York firefighter on 9/11; a soldier in Afghanistan; and a Brazilian on a tube train in London in 2005. The killing of Jean-Charles de Menezes is also portrayed in the most striking manner, with a tube-train whizzing across the wall, stopping, and muffled shouts preceding muzzle-flashes.

“I met his mother and father in Porto Alegre in Brazil,” reveals Waters. “That was very moving, as you can imagine, very emotional. Understandably, they were in floods of tears at the show, but they were at great pains to point out to me that, although he had been killed many years before, the thing that really sticks in their throat is that nobody in the British government has ever said they’re sorry. C’mon, guys, let’s have a little ‘sorry’, at least! That’s the least we could do, accept responsibility.”

The sequence in the performance was followed by a speech in which Waters dedicated the show to “Jean-Charles de Menezes and all victims of state terrorism everywhere”.

A section of Roger Water's show (Press image)

“Obviously, we do the show in many different countries, so for each place I get one of the local team to write it out in Croatian, or whatever it might be, check it, then get them to read each line out, and I write it down phonetically so I can read it out at the show. Not the French, because I speak French; but all the other weird languages, I’d have it translated that way so I could read it from cards. Some of the languages, god almighty – Polish is nearly impossible!”

Is the response to the show, I wondered, markedly different in those countries which have suffered overt state oppression within living memory, such as Russia or Argentina? “The response is different in each country,” says Waters. “When I’m playing ‘Mother’, for instance, there’s the line, ‘Mother, should I trust the government?’. If I’m singing that line in Greece, there’s a huge response, people shouting and cheering; but if I’m in Norway, they just stand there, puzzled: ‘What’s he talking about? Of course we trust the government – they look after us, we get free school dinners, education and healthcare. Why wouldn’t you trust the government?’ There’s that little Scandinavian corner of Europe, including Denmark and Holland, a cluster of genuinely socialist societies where they do seem to care about each other and look after each other.”

The main reason for revisiting The Wall as a live show, claims Waters, was his realisation of how different he was from 1979, when he was a relatively young man, in his thirties.

Pink Floyd - Richard Wright, Syd Barrett, Roger Waters and Nick Mason (Rex Features)

“Forty years later, I felt the piece could be more about our general dilemma,” he says, “and much less about the problems a rock-star bloke who’s going crazy might be encountering. I tried to make it a more general attack on tyranny, and on the constant waging of war, which seems to be the go-to mode, to the detriment of everyone who lives on this small planet. We need to point at this dilemma and examine it as much as possible, rather than just go, ‘that’s the way it is’.

“This idea of being constantly at war is a huge worry, particularly where I live in the United States, because the law is being eroded, slowly but surely, piece by piece. Who are we at war with? Terrorism? Well, you can’t be at war with an idea. But apparently we can, and there’s no open forum, these decisions just get made, willy-nilly, whatever the electorate might think of them.”

He remembers how he felt on 9/11, when he was working in a studio in London. “I was so naive!” he admits. “I actually thought that in the aftermath, when everyone was commiserating and supporting the Americans, that they might see it as a wake-up call, that they might become introspective in some way or another. How fucking stupid was I to even think that might be a possibility! When in fact it’s been used, as we now know, as an excuse to go and destroy the world.”

Clearly, he has lost none of the fire that drove his youth. Unlike Bob Dylan, who a few years ago admitted he no longer recognised the younger self that wrote incendiary songs, Waters claims that he still feels affinity with “poor little fucked-up Roger”, as he calls him in the documentary.

“Oh yes,” he says. “Y’know, when I sing some of it now, it still affects me the same way. I can’t sing that bit in ‘Vera’ without a tear in my eye: when I’m standing there onstage singing, ‘Does anybody else in here feel the way I do?’. I look out across the audience and go: ‘Yeah, I do!’”