Tony Blair in The Queen, David Frost in Frost/Nixon – and now Brian Clough. A weird choice, no? How long did it take you to decide to take the role?
A millisecond. He’s an amazing character. In public he was cocky, intelligent and funny, but in private prone to huge, angry tirades. He was immensely generous, yet frightening. Getting a handle on that was fascinating. The research and preparation took about three months.

Three months? Don’t you just use the same methods for each character?
The basics are the same. I immerse myself in their life, using TV footage, books and recordings to get as much real information as I can. Then with each character there are offshoots of research. For instance, with Clough, I started looking into cult leaders.

His teams were like a cult. He would totally dominate his players, taking clubs that were not doing so well or buying players who had been written off, then reshape and remould them in his own image, to leave them with a mixture of respect and fear for him.

Who did you study?
David Koresh, Charles Manson… anyone I could come across. I looked at their tactics and how their groups functioned. It was to get a sense of how you make people worship you.

You used to idolise old thesp Laurence Olivier yourself. How the hell did a kid from Port Talbot get away with that?
I remember seeing Olivier’s Richard III – his character was so disturbing it stayed with me, sparking my imagination all the way to stage school. I was lucky, though. I was the best footballer in my school, so no one took the piss about me acting.

Oh yes – Arsenal once tried to sign you. Did you do all Cloughie’s tricks in the film?
Absolutely. I’ve loved football since I was a kid, bunking off rugby matches to play, then getting punished. Mind you, the first day on set I felt a lot of pressure. I’d been telling everyone that I was much better than them and now I had to keep the ball up, turn and volley it into the top corner. I did. It was fine.

Were there kickabouts during breaks?
Sure, but I never joined in. I just walked past shouting at people every now and then. I don’t intentionally stay in character but once you start tapping into other people you can’t really switch that off.

And your next role is a Muslim terrorist?
Yeah. In Unthinkable I play a terrorist who gets captured and tortured. On my first day of filming, I turned up and got chained to the ceiling with a hood over my head, just wearing a pair of boxer shorts. Then they hosed me down with cold water. Welcome to Hollywood.

Ouch. Is that the worst thing that’s happened to you on a film set?
Nowhere near. I was once attacked by a group of llamas. That’s animal llamas, Tibetan monks didn’t rush me. But the worst was during a scene for The Four Feathers. Just as the director went, “Action!” a horse dug his hoof into my foot. It was the most painful thing I’ve ever felt. All I wanted to do was scream, but I couldn’t mess up the shot – every second of film cost thousands. When the director said, “Cut”, I had to be carried off the set.

Apparently it’s tougher to get you off a karaoke set…
Who told you that? Yes, I have a threesome I seed in throughout the night. There’s Sweet Caroline, then Foo Fighters’ Learning To Fly somewhere in the middle and then Sweet Transvestite from Rocky Horror to end.

Strange trio.
Yes, yes it is. And one I wouldn’t recommend to anyone else, but it works for me. I’ve got a friend who does ‘Kamikaze Karaoke’ – a game where you have to choose the most difficult song you can and then perform it in front of strangers. You can’t mess about. You have to get up and go for it. I wouldn’t recommend it.

So you’ve indulged?
I made a really horrific attempt at Livin’ On A Prayer by Bon Jovi and am still suffering the effects. It was far too high. Never again.

Nasty. Re-visiting torture, how would a torturer break you?
Very easily. Physically, my character was waterboarded in Unthinkable and I wouldn’t last a second. Mentally, make me watch something I’m in for the first time. Believe me, that’s torture.

According to some critics watching the Underworld films is torture…
Yeah, but there is a huge amount of snobbishness about fantasy and sci-fi films. A film should be judged on what it sets out to do by people who are into that type of film. Not by reviewers who never have and never will like anything in that genre. That’s pointless.

A bit like your dad being a Welsh Jack Nicholson impersonator?
Not at all, what he does is cool, hilarious. He’s always watching Jack in case he needs to change up his appearance. The year I went to the Oscars for The Queen Jack got up on stage and he was bald. I remember thinking: ‘Please Dad, don’t do it.’ Thankfully he didn’t.

Talking of the Oscars, why haven’t you had a nomination?
When it comes to awards, it seems people need to be told “this is acting” and so anything that helps that, like looking very different sees you gain recognition. For example when Hilary Swank plays a man or Charlize Theron does her role in Monster, people are instantly aware that there’s acting going on and they, often rightly, laud the performer for it. I don’t work like that. I want people to believe in the character not my acting. If I see myself acting, I see myself doing something wrong.

What do you mean?
I don’t like drawing attention away from the person I’m playing. I’ll lose or put on weight, get in or out of shape or whatever, but I prefer to use what I’ve got rather than adding to it, because I worry that adding things makes people too aware of what I look like. I want people to accept me as Brian Clough, David Frost, Tony Blair etc, not as an actor wearing prosthetics. Sticking things on distracts me, and if it distracts me it must distract the audience.

Who would you like to play Michael Sheen?
Sofia Loren is going to play her own mother in a film about Sofia Loren, so maybe I could play my own dad. As for me, Helen Mirren could pull off my early years, with Frank Langella to play the later years.

Sam Mendes described you as “fiery, mercurial, unpredictable”. Is that fair?
Yeah, I’d say that’s a fair description, though it’s a very positive one. I’m also deeply boring, lazy and apathetic.

The Damned United is in cinemas now.