But whatever his mental state beforehand, LSD wreaked unimaginable havoc on the 25-year-old Brian Wilson

Wilson began hearing voices “saying derogatory things”, telling him that he was finished and was going to die soon, a condition that continues to this day. “Every day,” he nods. “A daily struggle.” The voices were accompanied by black depressions and bursts of crippling, irrational fear. Fifteen years after they began, he was diagnosed with bipolar schizoaffective disorder: in the meantime, Wilson attempted to silence them himself with cocaine and heroin. Fifteen years seems a long time to wait before seeking help for such terrible problems, I say. He frowns again: “I didn’t need help before then.”

That isn’t what contemporary reports suggested. Meeting Wilson in 2011 might be hard work, but by all accounts it is nothing compared with meeting him mid-70s. It was about that time that the Beach Boys, desperate for a hit, announced that their errant mastermind was miraculously cured and sent him out to meet the press to prove it. The resulting profiles were heartbreaking and horrifying in equal measure, depicting a halting, visibly terrified man who said he “felt like a prisoner”: occasionally, the interviews concluded abruptly with Wilson asking the journalist for drugs. Equally, I can be thankful I didn’t meet him in the 80s, when he re-emerged again, looking movie-star handsome in a way he never had at the height of his fame, but with the ominous figure of Eugene Landy in tow, a therapist who had apparently nursed Wilson back to health at a cost of $35,000 a month, but who had also announced himself his manager, co-writer, producer, financial partner and beneficiary in all of Wilson’s professional activities, and to whom Wilson had an alarming habit of referring as his “master” (“And a good dog always waits for his master!” he announced cheerily to one dumbstruck hack).

He abandoned Smile unfinished, much to the relief of at least some of his fellow Beach Boys, most notably Mike Love, who was openly, vocally horrified by the music he’d made, and by Van Dyke Parks’ strange, impressionistic best hookup Ballarat lyrics

Eventually, Landy lost his psychologist’s licence and found himself subject to a court-ordered removal and restraining order (he died in 2006). “His life turned into a better place,” says Van Dyke Parks, “when he got a life companion, when he met that girl, his wife. Well, for better or worse, but certainly for richer not poorer, he’s had a great life.”

And thus Wilson’s unexpected artistic Indian summer began, largely guided by his second wife, Melinda Ledbetter, a former car saleswoman he married in 1995 and with whom he’s subsequently adopted five children

His solo career really took off in 2002, when he performed the Beach Boys’ Pet Sounds live in its entirety at London’s Royal Festival Hall, an event that was greeted with a kind of disbelieving hysteria by critics and fans, and that spawned a kind of mini-industry in its wake: you currently can’t move for artists performing “classic” albums in their entirety. Since then, he’s completed Smile, and released four further solo albums of varying quality. He plays music every day, he says, and tries to write something every month, but the songs don’t come as easily as they once did, he says, and a couple of years ago they stopped coming entirely. “I don’t know why,” he says, but it’s something that didn’t even happen at his lowest ebb: amid the bleakness of the early 70s, he somehow kept sporadically producing incredible songs: Til I Die, This Whole World, Sail On Sailor…

There’s always touring, however. Wilson’s touring schedule is fairly remarkable for any 69-year-old, let alone one diagnosed with bipolar schizoaffective disorder. As he says, it’s nothing compared with his early 60s workload, which given how that turned out is probably just as well.