Kit Harington can’t seem to stay out of war. While in his final year of school at Britain’s Central School of Speech and Drama in 2008, he landed the coveted role of Albert in the National Theatre’s production of “War Horse,” an experience he says “still stands as the biggest moment of my career.” Of course, he regularly goes into battle as Jon Snow in HBO’s hit “Game of Thrones,” such as this week’s epic battle at Hardhome. And now he can be seen on the big screen in “Testament of Youth,” an adaptation of Vera Brittain’s beloved memoir set during World War I.

In the film, directed by James Kent and hitting American theaters this week, Alicia Vikander plays Vera Brittain, while Harrington stars as Roland Leighton, her fiancé. Leighton becomes a soldier on the front lines, which is partially responsible for Brittain choosing to leave Oxford to become a war nurse.

Harrington spoke to Variety about what the movie meant to him, his hardest role to date and his recent forays into comedy – most notably a “Game of Thrones” musical sketch with Coldplay for Red Nose Day.

So among your many talents, you’ve just revealed to the world that you can sing!
Oh, really? People keep telling me that and they must have done some autotune to me because I swear I can’t sing.

Were you nervous to do the sketch?
Yes, I was. I got through the door and they said, “Can you sing this song?” Half of my brain said, Yes because it’s a good cause and I should make a d–k out of myself, and the other half of my brain said, No, what the f–k are you doing? Obviously, I did it. I thought the whole thing was quite funny. I mean, I got to do karaoke with Coldplay as my backup band, not many people can say that.

Were you familiar with the memoir “Testament of Youth”? Is it required reading in British schools?
Weirdly, it was required reading and that’s how I knew it. I chose to do English literature at an A level and this was on the syllabus of the war poets. I had an obsession, a real thing, for First World War literature, growing up. I knew this book so when it came through, I really wanted to do it. I opened in the first page going, “Please have done this justice.” And when I saw that the writer had, it was a no-brainer to do it.

When were you able to fit filming in during your busy schedule?
We shot this last year; I managed to squeeze my filming in in three weeks because I had to go on to another movie. I was so adamant I wanted to do this. I was doing another movie and there was a point where the dates didn’t work. Usually I keep a steady mind about these kind of things; if something doesn’t work, it wasn’t meant to be. But this one I was on the phone to my agents every day saying, “You’ve got to make this work.” It meant a lot to me, this movie.

Have you ever played a real person before? Does that bring a certain responsibility with it?
No, I haven’t. I thought I would have a ghost on my shoulder the whole time, but I didn’t. I was just very happy to have this source material, the book, to really find out who he was. And I had these letters he’d written, I could read them every day and remind myself of the kind of stupid and brave young man he was. He was a teenager experiencing first love while being shot at on the front.

Did you audition for Roland or was it an offer?
I auditioned for this, which felt extra special because nowadays sometimes it can just be offers. And I feel like I haven’t earned it and I like an audition. I read with James and (producer) Rosie Alison and luckily for me, I don’t think James watched “Thrones” so I felt like I really earned it. Then I read with Alicia – we knew each other but had never shared scenes together, and we loved working with each other.

Did James know your work at all?
I think James didn’t know much about me at all, which was refreshing to me because a lot of people see “Thrones” or they think they know who you are as an actor because of a character you’ve played. What was nice about this was James didn’t really know me from anything and I could come to it fresh.

You talk about that perception of you, but you’ve been playing with it recently such as playing Jon Snow on “Late Night with Seth Meyers” or doing the Red Nose Day sketch. Would you like to do comedy?
I’ve always loved doing comedy. But it’s a specific type of comedy, farcical stupid stuff that’s slightly offbeat and weird. I’ve gone out for romcoms, the classical, more prosaic comedies, and it just doesn’t fit me. I like going out there and doing something really stupid. I enjoy it and I’d like to do more of it, but I don’t necessarily fit into a kind of tamer comedy. My mum would love me to do a romcom. And I’d love to do one. Find me one set in Hawaii on a beach, I’ll do it!

You’ve also been parodied on “Saturday Night Live,” how did that feel?
If you ever get ripped off by “SNL,” and I have been, it’s just a great privilege. They showed Kit Harington and they had him playing this moody and serious actor who takes himself so seriously and I was like, “Oh God that’s what I’m like.” But I can’t help it.

What’s the hardest role you’ve had to play?
Jon Snow. Physically not as hard as Albert in “War Horse,” whatever actor is playing that role right now I feel for you, man. But Jon Snow is a difficult animal to play. He doesn’t say much, he doesn’t express much, he keeps to himself. It’s difficult to find nuance with. He repeats the same thing over and over: “I’m a man of The Night’s Watch…” And the noble ones are the hardest.

And your character has the worst of it, you’re always in the cold.
And if it’s not cold, they pump in the cold and fake snow. I don’t mind cold, when we were in Iceland it was minus 40 and I don’t mind that. It’s when we were in Belfast and they’re pumping in fake snow which gets in your eyes – it’s the effects on “Thrones” that are killer, the smoke, the bits of dust, the snow. Everything else is glorious.