AT THE end of our interview, Harrison Birtwistle pours a couple of glasses of whisky that contain at least five drams each. We’ve been talking about Raasay – the composer spent seven years living in the Hebrides in the 1970s – and he jokes that the reminiscing has brought out old island drinking habits. “I still know every inch of that place,” he says. “I mean, the way of the land. I used to go fishing. I loved the east coast, where nobody ever went.”

Now we’re at his current home in the Wiltshire village of Mere, approximately a universe away from the Hebrides. There is a pot of tea on the kitchen table next to the whisky, and a bowl of lemons, and a potent Camembert that I brought with me from London and which seems to have ripened precariously on the train. “Aha, I know just what to do with that,” Birtwistle said when I handed it to him, eyeing the label. After Raasay he and his family moved to France, an hour outside of Toulouse. He claims his French is about as good as his Gaelic.

Birtwistle was born in Accrington, Lancashire, in 1934, and though he left in the 1950s his accent is still intact. He’s notoriously laconic in interviews but today he is charming; anything daft or pretentious is met with a raised eyebrow, nothing worse. Could he see the Cuillins from Raasay? I wonder aloud, trying to picture the exact geography of the two islands. “Cuillin, singular,” he corrects me, eyebrow inching up. “And I thought you said you’re a hillwalker.” I ask how much time he spent with the Gaelic poet Sorley MacLean, who lived just across the Sound of Raasay on Skye. “Yeah, I knew him. My sons knew him better. They went to school in Portree.” He pauses. “You remember the first line of Hallaig?” This time I’m in better luck. Time, the deer, is in the wood of Hallaig.

For most artists, living seven years in a place of such extreme landscape and locals and weather and drinking capacity would likely have a direct impact on the character of their work. A few hundred miles to the north, an old friend of Birtwistle’s from student days, Peter Maxwell Davies, took up residence in a bleak croft on Hoy and wrote reams of scenic responses to the Orcadian seas and skies.

But Birtwistle balks at the notion. “I don’t believe in consciously expressing something,” he says. “Expression comes in spite of yourself. I don’t believe in inspiration – not specifically, in the sense of being inspired by something. I’ve been lucky enough to be musical, and maybe at one point I was inspired. But I don’t wake up in the morning and get inspired, like a movie of Van Gogh needing to paint the sun or something. It’s bloody hard work, writing music. Maybe that’s what inspiration is.”

The character of the island never came into his music? “Of course it came into my music! But I never sat down to write a Raasay piece.” He never composed a response to place? Now I’m fishing for irritating jargon: an aural evocation? A sonic landscape? “Bullshit!” he grins. “I don’t know what landscape sounds like, do you? Music is not mimesis. But” – he wags a finger – “I’m going to contradict myself now.”

Because he did write four Raasay pieces. A community piece called Roddy’s Reel (“community piece,” he mutters, “not exactly what I’m famous for”) and a string quartet called The Tree of Strings after a line from Sorley MacLean. The mysterious Duets for Storab is based on an old Raasay legend, and the monumental orchestral work Earth Dances on geological strata. “OK, I tried to put my relationship into it without getting all mystical or playing Scottish reels in the background,” he concedes. Since leaving Raasay in 1982 he has never been back to visit. “It would ruin the memory.”

Birtwistle will be in Scotland this weekend when the BBC Scottish Symphony Orchestra gives a rare concert-staging of one of his relatively recent operas. Premiered in 2000 by Daniel Barenboim at the Staatsoper Berlin, The Last Supper sets a libretto by the late poet Robin Blaser in which two millennia of Christian mythology are telescoped into a kind of friends-reunited scenario. A character called Ghost invites Jesus and his disciples “back into space/ time” to reconvene, 2000 years later. They chat about what they’ve been up to since the crucifixion. Judas turns up, against the odds. The piece contains classic Birtwistolian stage traits: ancient story, grand ritual, skewing of time and perception, confrontational, fiercely human, music drama.

Birtwistle grew up playing clarinet in local theatre bands around the Blackburn area and went on to study music in Manchester with classmates including Maxwell Davies, Alexander Goehr, John Ogdon and Elgar Howarth. Collectively they became known as the "Manchester School" – fiery agitators, rippers-up of rulebooks – and one thing Max and Harry shared especially was a predilection for rugged, ritualistic music theatre. They reworked old forms, fixated on stylised gestures, turned ancient myth into screamingly visceral drama.

Now Birtwistle laughs when I ask why he chose the Last Supper as subject for an opera. “I was inspired! And the inspiration – OK, I’m being silly – was that it was written for the millennium, to do with a specific date in Christianity. I’m not Christian, by the way. The Last Supper is a metaphor. About this position where one thing is here and the other there.” He indicates clock hands positioned either side of midnight. “Within no time at all, there is this artificial division.”

When the opera was first performed, many listeners were baffled by its narrative and moral ambiguity, its teetering stasis, its murky, ambivalent grandeur.

“I think people didn’t get it,” Birtwistle acknowledges. “It’s a tough grub. I think I have a reputation for difficult things. I don’t try to make my music difficult. I try to do things as simply as possible.” Did his own feelings about the piece change after the millennium? “I don’t think I felt anything. It’s like a birthday – in the end it’s a celebration of nothing.”

Does the piece feel especially timely now, with its exploration of Judas, blame, hindsight, wishing we’d done things differently?

“Yes, absolutely,” Birtwistle nods. “It’s what’s going on everywhere. Tony Blair. Brexit. Why did we let it happen? It’s a pretty human condition I guess.” He shakes his head. “I’m not a very psychological person. When it comes to analysing subject matter, I mean. I don’t get off on all that. I write operas about Punch and Judy, I write operas about Orpheus and Gawain. I like known objects. Stories we all know. When setting a myth, set a known myth, otherwise nobody knows what’s going on.”

He says he used to read a lot of trash. Pulp fiction. Crime thrillers. “Hardly anybody is any good at finishing things. I’m an authority on this. I used to get to the last two chapters then throw the book away. But it’s different if you know exactly what the story is about from beginning to end. Then it becomes about how you tell it, like telling a joke.” He glances up. “I could tell you a joke and you wouldn’t laugh. A comedian would tell you the same joke and you would.”

Try me, I say. He looks skeptical, then grumbles: “A penguin goes into a bar. And the penguin says, ‘I’ve lost my brother’. The barman says, ‘what does he look like?’” I laugh. See, I say. “Eventually you did,” he grimaces. “OK. A man is walking down the street with a penguin. Someone comes up and says, ‘you should take him to the zoo’. The man replies, ‘we’ve just been there. Now we’re going to the movies.’”

Harrison Birtwistle’s The Last Supper is at City Halls, Glasgow, on January 14