Trainspotting is 25 years old. Did you have any idea when you were writing it that it would become such a phenomenon, culturally and commercially?

Not really. The initial buzz it generated was among a certain section of the London cultural cognoscenti, the ex-punk crowd. They got it immediately. Because of the subject matter, which involved hard drugs, I thought it would become a cult book but not generation-defining, which is what other people have called it since. It’s strange, but it has taken on such a life of its own that when I see it on a shelf in a bookshop, it almost feels like someone else wrote it.

You’ve since written four novels with those same characters, including this year’s Dead Men’s Trousers, and there have been two films: Danny Boyle’s much-lauded Trainspotting (1996) and his reboot, T2 Trainspotting (2017). Renton, Begbie and the crew obviously still mean a lot to you.

Well, to be honest, I don’t think about them at all unless I’m writing about them. What I will say is that they were making choices that many more people are having to make now. They were facing a kind of existential crisis – what is the point of us if we are redundant? Back then, they were mocked – all those lost men without jobs, or community, or a shared sense of purpose. Now, that’s become very much a middle-class problem, too.

You live in Miami now. Do you go back to Edinburgh much?

From time to time, yes. I’m intrigued by how Edinburgh has since become a successful model for all UK cities in terms of so-called regeneration. Push the working classes out to the edges, camera-up the city centre and fill it with posh students, the ultra-wealthy and tourists. Edinburgh was always a working-class city, though not a proletarian, industrial one like Glasgow. That’s changed and most other cities have followed that model.

Why Miami?

It’s a big world and I’m a nomad. I want to see as much of it as I can. I live in Miami beach, which is pretty interesting. If I go for a walk, it’s full of people preening and strutting. Narcissism is embedded in the culture now. For a writer, it’s good to observe all that stuff firsthand. Plus, I’m pitching a lot of TV ideas right now so I’m back and forth to LA.

America is an interesting place to live right now. Are you worried?

There is definitely a sense of rising anxiety here, the feeling that there could even be an impending apocalypse of some kind. In a perverse way, it’s good to be in the midst of it. The novel I’m working on is about contemporary American shootings. It kind of makes sense to be here.

You have written about Scottish independence in an interesting way: you’re not so much a nationalist as someone in favour of the break-up of the United Kingdom. Looking from the outside, do you think that may yet be one of the unintended consequences of Brexit?

I hope so [laughs]. With Brexit, everything is up in the air. We have allowed our political institutions to be poisoned by greed and money and the corruption that ensues from that. It’s extraordinary how Corbyn gets vilified in the media for what are essentially old-fashioned, social democrat-style policies. Suddenly, they are being portrayed as extremist. The new narrative is globalists and nativists trying to wrest control from each other. I think that’s what politics is now essentially. And it’s technologically led, which makes it much worse – and much more accelerated – than in the past. It sometimes feels like we’re sliding into fascism by stealth.

What’s your solution?

Democracy is about ordinary citizens, not oligarchs, aristocrats, elites or indeed royals. We’ve lost sight of that. I think that the hierarchies that have been around for centuries need to be dismantled. We’re stuck with so-called democracies and imperialist states that simply don’t work anymore in what is essentially a conceptual society – we don’t make things anymore, we create information. I think we need to build new civic democracies, whether regional or global. My feeling is that the smaller states work better. Get rid of the idea of nationalism, even of countries. It doesn’t matter what you call somewhere as long as it works for the majority of the people there.

How do you think all this affects culture and art?

Well, I hear people asking, why do we need culture anymore? It’s just about communication now. So, my question is, what will happen to all the beauty and knowledge we traditionally found in art, literature and music? Will it no longer be of use in the advanced communication society of the future? What will happen to the things that moved, stimulated and entertained us? It sounds like sci-fi, but people are already going home to their sex robots. Where is love, romance, desire? All these notions are being challenged right now. It’s an interesting time to be an artist or a writer.

You were renowned for your somewhat hedonistic lifestyle when you were younger. You’re 59 now; have you settled down?

It’s controlled explosions these days. I’ll have the odd tickle if something interests me. It might get messy occasionally, but nothing like it used to. I’m pretty sporty these days. I go to a boxing club most days; it’s the ultimate workout. You feel alive at the end of it. We’re all getting older and heading towards death, but how much of your life do you want to spend thinking about that? I’d rather have the intensity of the boxing gym. It keeps you alert and alive.