Assassin's Creed was in gestation for quite a long time, and I remember hearing years ago you picked up the project. For a lot of people, it was quite a surprise. What was it that made you want to jump on board?

MICHAEL FASSBENDER: I had lunch with the guys from Ubisoft, and by the end of the lunch I was on board. Really, the world that they had created, this universe, I thought was fascinating. I thought it would lend itself very well to the cinema experience.

The first thing that really struck me was the concept of genetic material. That within all our DNA, we have the knowledge and experience of our ancestors – that we carry that. It has been passed on through the generations, and we might describe that as a sixth sense or a gut feeling or an instinct.

For me, that seemed really plausible scientifically. So I thought, "that's really interesting already that you can have this fantasy world anchored in something really real".

And then the world of Templars. You've got this elite group of society – powerful, rich people that basically run the world, and they believe in science and order. And they also believe that some humans are of a higher value than others, and in fact some of them should be enslaved.

In opposition to them, you have this brotherhood, this creed – the Assassins, who believe that free will should be protected at all costs. And actually, they date back to the Garden of Eden. The first two Assassins were Adam and Eve, and they used free will to pluck the apple from the tree.

So the apple is our artefact in this film. Of course, the artefacts exist in the game. Without going too much into it, the artefacts need to be protected from the Templars – because if they get all of them, then they're going to call back the Ancients, and that's bad news. [laughs]

You hadn't played the game when you came on board?

That's correct.

Have you since?

I have, yes.

Historically, a lot of video game movies haven't been great.Were you worried about that, and having to stick stringently to the games to please the fans?

I wasn't aware of it until people like you kept telling me [laughs]. They were like, "It's cursed".

There was a lot of, sort of, ignorance is bliss, in that regard. I don't really pay that much attention to those things. Either a film is good or it's not. We knew that we weren't going to be making a video game, because that just doesn't translate well to a narrative story or a narrative medium.

The thing with the video game is, you're in charge of what the character does. You choose the avenues the character's going to take. It's a much different interaction with the screen. Whereas, with this thing, we're going to take you on a journey.

The biggest challenge to begin with was how to distil this dense world into simple things that people could grasp hold of if they hadn't played the game – that they didn't have a backstory to this world coming into the cinema. So those were the things that we really concentrated on.

Templars – who are they? Assassins. The artefact – in this case, the Apple of Eden. The Animus – what that is. Genetic memory, of course. And then the parkour elements. And in terms of the action, we definitely wanted to keep that, because that's just cool [laughs].

You did a lot of your own stunts on this one, didn't you?

I did, yes. I did 95% of the fighting, as did Ariane Labed, who plays Maria. In terms of the jumps and obviously the Leap of Faith – I was kind of restricted in things like that.

Did you hurt yourself at all?

Just minor things. Nothing majorly, thank God. [taps table]

Do you have a favourite way of killing people in the game?

I guess the knives. It's nice to get up close and personal [laughs]. I think as an assassin, that's the ultimate level that you can reach to get close to your mark. That was something, of course, I was biased towards – because that's Aguilar's weapon of choice.

And I like a little bit of bow and arrow action, just because I've always liked it since I was a boy. I dabbled around with that. So that's fun.

And, of course, you're playing two different characters in this. How was that for you? How did you approach it? Did you build a full backstory for Aguilar?

You usually do that with characters that you don't have real source material on. So yes, absolutely you do that. We started with Aguilar – so a lot of stuff at the beginning was just about getting the Spanish in order, and the physical elements of the character.

Because, really, a lot of the action sequences take place in the regression, and Aguilar is a man that expresses himself best through action. So it was very physical. I got to concentrate on Aguilar. And then, I dealt with Calum. So really, it was compartmentalised quite nicely for me.

What was cool about the characters is, Aguilar is somebody who is on a path. He belongs to the brotherhood. He's willing to sacrifice himself for something greater than himself, for this belief system.

Cal is somebody who's been in and out of correctional facilities his whole life. His parents were taken away from him at a young age. In fact, when we meet him in the film, he's on death row. He's about to be executed. He's somebody who's very distrusting of people. He's quite cynical. He's definitely more of a lone wolf, as opposed to a team player. He's kind of the classic reluctant hero.

The games are set in lots of different time periods. Will you be tapping into that if you do sequels?

Absolutely. It's a huge part of the game. It's something that is key, I think, to it, and it's something we really enjoy doing. So we had an idea of what would happen over three stories, basically, when we were starting this one.

It'll still be Cal, but not Aguilar...

Perhaps. It'll be a different time zone, for sure. A different regression, yeah.

You have Alien: Covenant coming up where you also play two characters.

I know. What the fuck? I'm getting greedy, aren't I? It's an ego scenario, here. I just realised that after wrapping Alien. I was like, "Damn, I've been playing two characters in both films."

Obviously, we needed that in Assassin's Creed, because you need the ancestral link to the character in present day. But in terms of Alien, that wasn't really in mind hands. That was just written as it was.

What was it like working with Ridley again, a second time?

It's a blast. Ridley's a one-off. He's just such a master at what he does. He's become a really good friend. We have a lot of fun on set. I just try and learn as much as I can from him, because in all aspects of this medium, he's got such a wealth of knowledge.

Is Walter quite different from David?

Yes.

But they're both androids?

That is correct, yeah.

Is there anything you can say about how they all fit into the timeline?

Yes – I'm not sure what I'm allowed to say. Well, he's definitely a servant of the ship. We're coming to a period after Prometheus.

David is the only survivor?

As far as we know. Well, there was both David and Elizabeth. But the thing is, obviously, there's been modifications to the robots since then. So there's been developments because of some of the things that David had that perhaps were a bit worrying for people – the characteristics.

You've also wrapped now on The Snowman, can you tell me something about the tone? Is it going to be more like your 'grip-lit' Gone Girl-type thing? Or is it more in the Headhunters kind of zone?

It's got that Scandi-noir element to it, for sure. I think it's going to be very rich. I love working with Tomas Alfredson. He's an absolutely great filmmaker. And I think it's going to be scary, and I think it's going to be edge-of-the-seat stuff.

I like it because Harry Hole's a very flawed genius in his department of work. He's an excellent detective. But he kind of goes off the rails. He's very human in terms of—

Let's say, if there was a fight sequence with somebody. He's not Jack Reacher. He comes off the worse for wear a lot of the times in these encounters. And I like that. There's something kind of funny about that. I find that there's really comical elements there.

How about TV – would you ever fancy doing a part in something like Game of Thrones?

Erm... you know... I don't know. To be honest with you, I've been working on the Irish Myths for quite some time now. That's not the same as Game of Thrones, but it's of the same world, so I'll be concentrating on that.

Is that TV?

That will be for the cinema. That will be the movie.

What can you tell me about that?

In Ireland, we've got this mythology. You could find parallels to Greek mythology, but it's just a very rich world. You've got characters like Cuchulain, who's in some ways a parallel to Achilles, but is a Gaelic version. It's just a very rich world where, again, men and women fight as equals alongside each other – the connection to nature and the animal world is a very real one.

It's a very rich world, and there's just so much there we learned as kids in Ireland. It's been something I've been really dying to bring to the big screen for a long time.

Is there anything you haven't done that you would love to get your teeth into?

I'd like to direct at some point.