If you like your stage literature strong and salty, your scenarios macabre and brutal and your plays epic, cerebral, and spiced up like cauldrons of medieval bile, you'll warm to the veteran conundrum of the English stage, Howard Barker, who returns to Dublin with The Wrestling School, the company devoted to his uncompromising work, which he now directs himself.

Although produced in Vienna in 1998 in German, He Stumbled is now enjoying its first English-language production. A far stranger creature than his most successful play, Scenes from an Execution, it's an appalling tale of a famous anatomist who comes to disembowel the dead King's body, only to be ensnared in a deadly sexual flytrap.

Barker: "The idea came to me when I visited the vaults in Vienna, where the Hapsburgs are divided up into small parts and bottled. That idea of the relic quite intrigues me . . . "

A very Catholic phenomenon, I remark, still perplexed by the play: "Yes, but not only. If you take the Unknown Warrior, it's not an English or even a Roman thing. It's the bringing back of bodies, the insistence that a mother must find a dead child, this huge religious investment in the flesh. Here, it's about the dissemination of the royal body to certain key chapels in Europe which occurred in the 17th century . . . " His mind switches directions. "The odd thing about material religions like Communism, of course, is that they nevertheless believe in the sanctity and preservation of bodies. Look what happened to Lenin's body, Stalin's . . . "

It's this odd mixture of obsession with royalty and revolution which makes Barker maddeningly difficult to tie down. We meet in Brighton where Barker has lived for 20 years, for afternoon tea (Earl Grey) in the dingy, imperial grandeur of the Grand Hotel, where the IRA almost murdered Mrs Thatcher in 1984.

I smile bleakly when Barker says "I never invite criminals or journalists to my house". He is most amenable, however, folding himself up like a praying mantis in the big chair, keen to promote "the work" in his imperious, didactic tones.

The prolific 54-year-old Barker is an outsider in the English theatrical establishment. While his vast repertoire is enthusiastically performed worldwide, the RSC hasn't touched his plays since the early 1980s, and he has never had a production at the National. During the 1970s, Barker was lumped in among such lefty social realists as Brenton, Hare, Edgar, etc. But according to Barker, "I rapidly lost interest in churning over the usual contradictions of English class culture. One of the things that nauseated me was the regime of naturalism. Secondly, the obsession with satire in England, coupled with the national obsession with comedy.

"So my move to Catastrophism" - his own classification - "and tragedy came from a sense of nausea rather than a creative act of will. There was a conventional wisdom that tragedy was impossible. But in fact, the more hygienic and politically correct the society becomes, the more the necessity to look at instinct as the root of all behaviour."

Over the 1980s, in earthy historical plays such as Victory, set in the moral ruins of Restoration England, Barker's work mutated into what the veteran Guardian critic Michael Billington described to me as "untethered allegory". However, Barker has never lost his taste for symbolic sexual desecration, let alone his verbal sweetmeats of caustic venom, which scour the human condition. "The primary instinct that drives my plays is sexual love, the definition of self through passion. It's about the delicacy behind that clamouring."

It's also about rather queasy equations of power, voyeurism, jealousy - "It's a Jacobean thing: the plays are not responsible - while this culture is all about being responsible, so theatre becomes social therapy. You get plays in prisons, hospitals, schools, all about making people healthier. For me, theatre makes you unhealthy. It's an infection." I object, and he mentions a prison production of his, The Hang of the Gaol, "which was very much liked in Wormwood Scrubs a few years ago. But it's not principally the business of theatre to help people. It's about going into a dark space, not a light space, where what is legitimised is the darkness in you.

"You couldn't be less Brechtian than I am. Brecht said the audience must discipline itself, by continually looking at itself to see whether it's reacting properly - it becomes, literally, like an Enlightenment class. Mine's the opposite. Even physically I want a dark auditorium."

Interestingly, many of his premieres happen in translation in Europe. There's one coming up in the National Theatre of Denmark, and an opera libretto for the controversial Danish composer/director, Jacob Shocking. "I often wonder why the Danes, who have a very civilised welfare state and society, take to my bleak work. On the surface they're extremely civil, which I love, civil society."

When I express a rather darker vision of the Danes, Barker is delighted. "But that's very beautiful: somebody who has beautiful manners, and yet inside them, has this incredible aggression. That's the beautiful side of a human being. Not someone whose morals are . . . organised." He flashes a cold smile.

When I remark that some of his women characters are quite male, he says, "I don't think a feminist would say that. Women's sexuality is so powerful. It's so ruthless and quite destructive. I suppose in conventional terms women don't normally articulate their sexual needs in quite the way men do, but that's to do with the seen and the unseen. Sexual passion unlocks so many things, that people don't react in their socialised condition."

Interestingly, he cites his mother a few times. "I owe my vocabulary to my mother and my grandfather, who spoke a very particular form of London slang. When my mother spoke - she died last year - I could hear the 16th century in her, and that's because she was a working-class Londoner. I'm not middle class, you see. If you read David Hare, you wouldn't find any of those notes in there at all."

Barker grew up in post-war Norwood in South London. "My mother sent me for elocution lessons, which is why I sound like I do - it's one of those contradictions in my life which probably explain a lot of things. My father was a machinist in a factory which made Letts Diaries. He used to stick hard backs on my early Penguins to make them last longer. You can't ask a father to do more than that for a boy. So, in a way, he was a bookbinder, and my mother worked in various shops, and we lived in a council house."

Barker had one brother, a banker now retired in South Africa and suffering from Parkinson's disease. They are in contact, but not close. He studied history at the University of Sussex, near Brighton, where he wrote long, unpublished novels, then radio plays for the BBC, before he moved to the stage. He still writes for radio, and has just finished "a rewrite of Snow White called Knowledge and A Girl. Grimm's tales mean a lot to me - again, non-English literature.

"I speak English, I've got English mannerisms, but really my cultural instincts are somewhere in the Black Forest. They punish people in Grimm; that's a simple moral code I can respond to. There is this beautiful un-English ending to Snow White, where the mother is forced to dance to death in red hot shoes. That's a fascinating reversal of the erotick" - he emphasised the "k" - "isn't it?"

Barker and his former wife, a schoolteacher, divorced when his two sons were young, but they closely co-ordinated the rearing of their two boys in Brighton. One is reading history at Cambridge, while another has a philosophy degree from UCL. Barker still lives alone, in the old house. "Brighton was a kind of test tube for the whole Thatcher social experiment. It's a very money-oriented fantasy land, with a huge drug population and beggars in profusion, lots of crude entertainment. It's a kind of grotesque model of Thatcherland, or Blairland now. It doesn't do anything: nobody makes anything. It's kind of shabby and criminal."

I keep returning to politics, trying to figure out was Barker a radical, a neo-reactionary, even some tormented royalist? "Well, my father was a Stalinist, so I was brought up very much on the authoritarian left, and that permeates the earlier work." How did he react to the Thatcher years? "My sense was that she took the fig leaf off the Left, and there was very little behind it. So little that the present soul-less government we have is merely her offspring. They're all lawyers, and God help a country governed by lawyers. Blair's a lawyer, so's his wife, Straw, at least 50 per cent of them . . . I'm not sure if Robespierre would have been quite so unpleasant if he hadn't been a lawyer."

But what is Barker's obsession with the physicality of the monarchy? "The King's body is the State, or certainly was when royalty was significant socially. For a dramatist that's a fine metaphor, and it was very useful for Shakespeare - the Queen is virtue, the King is the State, so you set up the two deeply significant symbolical bodies . . . "I'm very interested in the way the King and Queen here have total permission, and they have licensed themselves beyond the norm. That's something really that only privileged societies can do. For example the Marquis de Sade belongs in a climate in which only someone like he can do that. Today we think anyone can be the Marquis de Sade . . . that's democracy for you."

That's the thing about Barker: you never know when he's being ironic, or just poetically provocative. But why does he keep returning to, quite literally, a dissection of royalty? "Probably, because in a funny sort of way, somebody has to represent the inequality of nature. That's why republicans have to demolish it and behead the king, the symbol of natural inequality."

For all this engagement with the big themes in history, Barker despairs of contemporary English theatre, which "relates everything directly to the issues of its time. And English critics don't like trying to come to terms with a moral argument. They want to see empathy. But there's no empathy in my work. You don't recognise your auntie in my plays, which is what so many realists are always trying to conjure up. I'm pushing a different frontier . . . saying things which are not normally said, trying to enter the audience through the rear of their consciousnesses.

"I don't think people have written that kind of tragic way since the 16th or 17th century, because of the Reformation. I mean, Shakespeare's right on the edge of the Catholic period. After the Reformation, it becomes all about English moralising, utilitarianism, welfare, and now therapy. You have to go back to the 17th century before you get irresponsible, violent, seismic writing, which comes from the viscera, not the head."

We get talking about literature, and Barker's "passionate involvement" with Theodor Adorno's Minimalia Moralia. "It's a fascinating image of a rich bourgeois mind, who loves hotels and restaurants, trying to be Marxist, it's a beautiful struggle."

Suddenly he sits forward. "Do you know, is it true that Adorno died of shock? He was very popular in the 1960s with all the German Left feminist people. But I understand he was on a public platform, and two young women rushed up and pushed their breasts into his face - I heard he was damaged by that. Considering how much he believed in passionate sexual encounter, it's an ironic fate . . . "

As we talk, we are suddenly swamped by a wedding. An old lady, her devastated face wearing a deceptively daft-looking Queen Mother expression, wafts past under a vast hat. "Fellini," declares Barker.

Soon after, he abruptly ends the interview and moves away, filter-feeding through the wedding rabble, leaving me free to navigate Brighton's seafront, with its late-season hoopla hucksters, dodgy charity collectors and jellied eels, my view of the world rather chilled and shaken by the very civil Mr Barker.

He Stumbled runs at the Samuel Beckett Theatre from October 9th to October 14th at 8 p.m.