It is “fair enough”, Aidan Gillen says, that people mainly recognise him as the bad guy: his best-known roles tend to be villains. In his hometown of Dublin, it is always the fearsome John Boy from Irish gangster drama ; meanwhile , in which Gillen played hitman Aberama Gold, is apparently “very big with Eastern Europeans”. 

Having also starred as two of the slipperiest characters in two of this century’s biggest TV shows – corrupt politician Tommy Carcetti in and nefarious string-puller Littlefinger in Game of Thrones – it is no wonder that the 58-year-old actor is often clocked in public. At the height of Game of Thrones, he enjoyed it – “It was so huge, you just had to give in to that. It was fun” – but the first thing he tells me is how much he hates doing interviews in busy restaurants “with people at the next table leaning in to see what you’re gonna say”.

Thankfully, our interview is over video call from his Dublin home, and Gillen is chatty, if occasionally
veering into wind-up territory. When I ask what he has been watching lately, he says “back-to-back and ” with a glint in his  eye.

His latest role is in the BBC and Irish national broadcaster RTE’s , a “heightened, cartoonish” crime caper from The Thick of It’s Chris Addison and writer Stuart Carolan, with whom Gillen worked on . The series follows two young care-home workers, Bridget (a “sharp as f**k” Ella Lily Hyland) and Paul (rapper-turned-actor Casey Walsh). When a patient played by Gillen claims to be Grinner McNair, a tattooed gangster who knows where a hoard of long-lost Celtic treasure is buried, the pair become embroiled in a chaotic, violent and darkly funny Bonnie and Clyde-style escapade. 

Grinner spends most of the first episode in a coma, but once he wakes up, Gillen brings an unsettling mix of charm and fizzy volatility to the screen. He is fond of the “hardchaw” character – “it means Dublin hardman, but likeable” – and based him on “a few guys I see sitting outside this particular pub, as the sun beats down at two o’clock in the afternoon on a Tuesday”. 

The appeal of working again with Carolan, Gillen says, is that “he’ll go up to the line and then he’ll cross it”. Reflecting on , he says: “There was a lot of stuff that was definitely crossing the line of what people thought might be acceptable as primetime viewing. Not just violence – the stuff that people were saying, phrases that people were using, they were really quite transgressive. There was some quite creepy stuff with bones. It was dark – shooting cats with machine guns, you know? Stuff that a more cautious broadcaster might have gone: ‘Well, we can’t have that’.”

He had hoped for more boundary-pushing in and was rewarded with a fairly eye-popping scene involving horse viagra and a character played by Irish “literary great” Patrick McCabe (who, incidentally, lives three doors down from Gillen): “I loved it. That was my favourite scene… If you put that on the table, it’s not Chekhov’s gun. It’s Chekhov’s horse viagra.”

Gillen is no stranger to statement-making television. In Russell T Davies’s 1999 series , he starred as Stuart, a thirty-something gay man who starts a relationship with 15-year-old Nathan, played by Charlie Hunnam. “There’s a lot of tricky elements of what was going on with my character and him and ages and consent,” says Gillen. “Tricky. Messy. But not unrealistic.”

The show was a watershed moment for gay representation and featured graphic sex scenes in a time before intimacy co-ordinators were commonplace. Does Gillen think it would have helped to have one? “ didn’t really need it,” he says. “Probably because the director, Charles McDougall, had some experience. I remember him saying: ‘When it comes to these scenes, everyone [on set] is gonna f**k off.’ I learnt from him that it was about being matter of fact: ‘This is what we’re gonna do.’”

On the set of a few years later, Gillen was grateful for the advice: “That’s exactly what happened – everyone disappeared and I had to take over. I was the intimacy co-ordinator but I was in the scene also.” He does however suggest that the addition of an intimacy co-ordinator “can take over a little if you’re not careful, and make it a bit dead. But it should be available”.

Not that he is likely to need one himself any time soon: “The last thing I want to be doing right now is sex scenes. It has come up a bit and I’m like: ‘Really? F**king leave me alone. I did that shit when I was 23’.” Instead he is relishing the more lived-in roles that he has been looking forward to since he started out: “My favourite actors were a lot older and more character-based. I just thought the things they got to do were more interesting than running around kissing girls or whatever these juvie leads were doing. Romeo and Juliet – I don’t know what the f**k they were up to.”

If it seems as though Gillen has a gift for choosing compelling roles, many of them have somewhat chosen him. Sharing one scene with Harold Pinter on the set of Jez Butterworth’s 1997 film led to Gillen being cast in the Broadway production of Pinter’s r, where a producer of was in the audience. And it was that convinced Game of Thrones showrunners David Benioff and DB Weiss to cast him as Littlefinger. From there, he ended up as the baddie in the films.

“Even the fact that I’ve had a career at all is maybe an unusual set of circumstances,” says Gillen. “Not being good at auditions, not being a trained actor, not caring what people think.” His own favourite parts are, perhaps surprisingly, those in the “trashy thriller with a wrestler category”: being hunted down by Jason Statham in or “blowing up houses and kidnapping people” with John Cena in 12 Rounds. “It’s just fun to do and also not what people expect,” he says. “People think I should be doing the Royal Shakespeare Company, Troilus and Cressida or whatever.”

He concedes that post-Game of Thrones, some of his roles became “a bit same-y” – what Michael Gambon called “smash and grab jobs”. “Do you want to come to South Africa and play the villain in this? Here’s your hotel, here’s your per diems, it’s lovely and sunny,” says Gillen. “You’re still trying to do a great job, but this is not the vocational part of your craft.”

That said, he is not averse to adding a few more wrong’uns to his resumé in future. When we speak, the great James Bond debate is once again raging and with Gillen’s old writer Steven Knight at the helm, could he be tempted? “Well it’d be a lot more interesting being a Bond villain than being Bond,” he says. “And you’ve only got to do one film because you’ll get f**ked into a volcano at the end.”

‘Tall Tales & Murder’ is streaming on BBC iPlayer