Gabriel Byrne doesn't like the epithet "brooding" – the Irish actor famous for brooding in films such as Miller's Crossing and The Usual Suspects has repeatedly said so in interviews.

Instead, I think of that exemplary movie writer David Thomson and what he wrote about Byrne in his New Biographical Dictionary of Film: "Somehow, I always have the urge to reach out and tickle Gabriel Byrne," he explained. "I think it's because his uncommon aura of gloom and sadness seems so complete it likely masks a teaser or practical joker."

Reaching out and tickling Byrne seems a little presumptuous so early in our acquaintance, so I remind him that when he played therapist Paul Weston in HBO's In Treatment, another journalist dubbed him Dr McDreamy. "Oh, God… what can you say?" he asks, rolling his eyes.

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Byrne is seated in a club armchair in a central London hotel, alert but relaxed in the way familiar to In Treatment viewers. He's 63 now, the Dr McDreamy looks maturing well, but until middle age, the gloom and sadness were all too real. Thomson didn't know it when he wrote that entry on Byrne in his dictionary, but the "uncommon aura of gloom" was masking not a joker but a victim of childhood sexual abuse.

Byrne revealed on an Irish chatshow in 2011 how, between the age of eight and 11, he was sexually abused by Christian Brothers in the Roman Catholic seminary where he was studying to be a priest. "I didn't think it severely impacted me at the time," he told broadcaster Gay Byrne. "But when I think about my later life, and how I had difficulties with certain issues, there is a real possibility they could have been attributable to that."

Now, he says, his matter-of-fact tone less one of calm acceptance than of well-controlled anger, "Whether the Catholic Church attracts paedophiles or whether the Catholic Church itself breeds paedophiles, I don't know the answer. But because of this culture of secrecy, and because there's no accountability, priests – and nuns – could commit crimes against children and realise they didn't have to pay for it – the Church would never hand them over to the legal authorities. I think anybody who betrays the trust of a child deserves to be punished.

"A child doesn't have the understanding of the world to know what's really good or bad," he continues in this generalised vein. "As far as they're concerned, what an adult tells you to do is the right thing to do, and to take advantage of that is a crime against the soul of a child."

A long-term resident of America, Byrne returned to the Dublin of his abused childhood earlier in the year to film Quirke, the BBC's adaptation of John Banville's 1950s-set thrillers, which Banville writes under the pseudonym of Benjamin Black. "Crashing into the past" is how Byrne describes the experience. "By absolute coincidence we filmed in the very first apartment I ever had, on Pembroke Road," he says. "We shot in the theatre where I made my first professional appearance – I hadn't been in there since – and to walk into it… phew! Déjà vu doesn't begin to describe it."

Byrne's character, the eponymous Quirke (we never get to know his first name), is a pathologist at the Dublin city morgue. "Quirke was originally 6ft 4in, had the feet of a dancer and blond hair," says Byrne. "And I said, 'John, I'm really sorry but I'm not that.' And he said, 'It's curious… since you started to do this I've started to darken Quirke's hair and make him a little smaller.'"

Actually, I tell Byrne, I read the first Quirke novel to be adapted in the series, Christine Falls (in which orphaned Irish babies are clandestinely shipped over to a Catholic families in America), in the knowledge that he would be in the role. He seemed a perfect fit for the character Banville had written, while Andrew Davies' adaptation recreated remarkably faithfully the pictures that had appeared in my head. "That's good to know," he replies.

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Both Byrne and Banville, who are old friends, grew up in this Ireland of the 1950s. "It was almost a Taliban-esque society," says the actor, recalling an incident when his mother, who was walking down the street with him while pushing a pram, stepped off the pavement into the road to make way for a priest. "That's how much power they had. Now all the rocks have been lifted and all the maggots have crawled out. The Catholic Church is a tyrannical, evil institution, there's no doubt about it – anti-woman, anti-homosexual, anti-love, anti-condom, totally elitist."

His father was a cooper's labourer, making wooden beer barrels for Guinness, but his skills were made redundant by the introduction of the steel barrel. "So we had this strange situation where my father stayed at home and my mother went out to work (as a nurse)," says Byrne. "I was the eldest of six. I left school at 15 and worked k as a messenger boy in an insurance business in Dublin. Then I started to study at night and got a scholarship to university." He graduated from University College Dublin with a degree in archaeology and went into teaching until he was 29. It was then, having jobbed around in the Dublin theatre scene, that he won a role in the soap The Riordans – a sort of Irish Emmerdale.

"I got pretty successful in Ireland fairly quickly," he says. "I did a picture with John Boorman [Excalibur] and I came to Britain and made a film called Defence of the Realm [a 1986 political thriller, and a prime slice of Greenham- Common-era Cold War paranoia]. "I saw that picture recently and it really holds up except for one thing which is that there's a scene in which Denholm Elliott as a journalist is mystified by the technology of the tape recorder." We both stare at my tape recorder – digital now, of course.

London in the 1980s – a time of IRA bombs and Maze hunger strikes – was an inhospitable place for a young Dubliner. "To be Irish at that time was scary because you couldn't express an opinion about what was going on politically in Britain because people would turn round and say, 'What are you talking about? You're Irish.' There was a programme on television called The Comedians, and the bulk of that was just Irish jokes. You were allowed to be an entertainer, like Henry Kelly or Terry Wogan… a bit like the blacks in America."

Not surprisingly, when America beckoned, Byrne jumped. In 1988, he moved to New York to marry the actress Ellen Barkin, whom he had met while making the indie movie flop Siesta, and where their two children, Jack, a 23-year-old musician, and daughter Romy, 21, still reside.

He and Barkin divorced, amicably, in 1999, by which time Byrne had had his two greatest critical successes – as Tom Reagan in the Coen Brothers' Miller's Crossing, and as Dean Keaton in The Usual Suspects – while averaging at least four movies a year. Of which is he most proud?

"I'd look back on Miller's Crossing, The Usual Suspects, Jindabyne [an Australian adaptation of a Raymond Carver short story co-starring Laura Linney] and Spider [the 2002 David Cronenberg thriller]." What about In Treatment, which reinvigorated Byrne's career in the mid-Noughties and won him a Golden Globe? "Not really," he says. "Although it was tremendously difficult, like doing theatre every day. It was just two people so you had to be on camera all the time for the other person, so there was never any break in it.

"For me, the whole series was about listening, and listening is interesting to act on camera because it's quite difficult; if you're on take 15 or 16, it's very difficult to be acting with the same kind of engagement you did on take one."

A therapist was a nigh-on impossible role to research, he says, because it all goes on behind closed doors. "Like the confessional, you know. I kind of stumbled on the answer the night before we were due to start shooting – I was in a panic about it, thinking how am I going to do this? Then I was passing a café and saw these two people sitting in the window and this woman was talking animatedly to this man and he was engaged in the act of listening and I looked and thought, 'Wow, he's really listening to her.'"

Byrne hasn't undergone therapy himself ("There's this idea, in the words of Oprah, that you confront, you resolve, then you find closure and you move on… well life isn't as simple as that"), but therapists are among Byrne's biggest fans, and the least shy about showing it. "The shrinks are the ones who keep accosting me in the street. I kept thinking to myself, 'My god, why would anybody pay this person $300?' Really some of the maddest people I've met are shrinks. Also, people were telling them that they'd been going into therapy because they'd watched the programme, and [they would] say, 'Paul Weston would never say that…'" I tell Byrne that my wife is studying to become a counsellor and that In Treatment is recommended viewing for the course. "God help her," he says.

Byrne lived in Los Angeles, that home of therapy, for eight years, but left as he found it melancholy – "There's a tremendous sense of transience there, and what most people want to grasp is slightly out of their reach" – returning to New York. "There is a much greater similarity between Dublin and New York than between London and New York," he reckons. "I lived in London for eight or nine years and I found London has a peculiar energy, chaotic and fragmented, maybe because it's a series of villages. It's a difficult city to come into."

Byrne's other journey, from indie films to TV drama, mirrors the trajectory of many of the more intelligent movie talent. "I used to work in independent film but it doesn't really exist any more," he says. "Writers are moving more to television; franchise films have taken over in cinema. There's little in the way of complexity – bad guy, good guy, orchestra, the end – teenagers playing computer games in the foyer, which is packed with corporate sweets, and five minutes of the most appalling advertising that you wouldn't have watched if you were at home."

His latest TV role is in the new costume romp from The Tudors creator Michael Hirst, the History Channel's Vikings, in which he plays a Norse chieftain. "The 10th century, medallions, moustaches and long hair," is how Byrne summarises it. "Thank god I didn't have to do too much plundering and pillaging – I just sit on a throne and tell people to plunder and pillage."

Rather more challenging are two films he shot in France last year, one for Costa-Gavras (the veteran politicised director of films such as Z and Missing) and the other a romantic drama ("a French Brief Encounter") called Just a Sigh. "I've always wanted to be in a French film, like I've always wanted to be in a cowboy film," he says. "I've always wanted to get off a horse, tie it up and walk into a saloon. Steven Spielberg said to me once, 'I never know what you're going to do next… your career is completely under the radar.' And it's kind of true. I really like it like that, to be honest."

'Quirke' begins on BBC1 later this autumn