Let’s get this out of the way first. Kit Harington doesn’t hate Belfast. A few weeks ago the man who plays Jon Snow, sad-eyed bastard son of Ned Stark in

Game of Thrones

managed to annoy certain Northern Irish people by making the sort of joke certain Northern Irish people make all the bleeding time.

You remember. Harington suggested that Belfast, where much of the series is shot, was a nice place to visit for a day or two (but only that). He quipped that the tourist board was overly obsessed with miserable attractions such as the Titanic and the much-bombed Europa Hotel. What's the problem? He was only sleggin'.

Well, this is the Age of Offense. A few days later the poor fellow issued a sincere apology to all the recreationally outraged ninnies (my words, not his).

“I thought that it was all fine because I know people in Northern Ireland have a great sense of humour,” Harington says with less weariness than might be expected. “I had joked a lot with my Northern Irish friends on set about that. But I didn’t think how it might affect the tourist board, which was short-sighted of me. So I actually wanted to apologise for that. I think Northern Ireland is an amazing place. I go there every year and it’s a second home for me.”

I mean, it’s not as if he’s from Rio de Janeiro. Now 28, Kit Harrington was born in London but spend much of his childhood in historic Worcester. What’s so exciting about Worcester? Huh? Huh?

“Well, I can tell you right now that Northern Ireland is a lot more interesting than Worcester,” he laughs. “I think the places you really love are the places you joke about. I can joke about London. I can joke about Worcester. I can joke about Northern Ireland. I consider them all as home.” (The Worcester tourist board will, if offended, know whom to contact.)

Bourne of the Midlands

The HBO adaptation of George RR Martin's roman-fleuve has had such resonance that it's disconcerting to encounter Kit Harington in contemporary dress. Yet there he is in the big-screen spin-off of a popular (2002-2011) BBC spy series.

Spooks: The Greater Good casts him as a former agent who returns to the fold when his mentor (played by furrowed Peter Firth) disappears in mysterious circumstances. Harington gets to kick bottom, leap roofs and disentangle double-crosses like a west Midlands Jason Bourne.

“It was a lot of fun to shoot something like this,” he says. “I really wanted to do something contemporary, something quite modern. This fitted the bill quite nicely.”

It looks like a pretty physical job. Obviously, stunt men are on hand at all times, but there must be accidents. I had read that Harington banjaxed his ankle on Game of Thrones. How did that come about?

"Oh, I did it on my own time," he cackles. "I am absolutely safe on film sets. That was all my own fault. I did my ankle in climbing through a bedroom window trying to rescue my keys. In Spooks, I climb a balcony. I sent a photo to the Game of Thrones producer saying: 'Look, I am trying it again.' I didn't get the answer I desired. Ha ha."

One can understand why a sense-of-humour bypass might set in. Game of Thrones is a phenomenon, and Jon Snow is one of the few genuinely nice characters in a series packed with psychopaths. Saddled (or blessed) with the sort of eyes that always seem on the point of tearing up, Harington brings real poignancy to the role of the misused illegitimate son.

If this were another series, we'd suggest that the producers wouldn't want to lose him. But in Game of Thrones no character is safe from annihilation.

“We have seen them come and go,” he says. “And I have been there since the pilot. It is odd that there’s this declining group of actors. I realised that when filming this year.”

If Harington were a similarly well-liked character in, say, The Good Wife, he could count on being there for years to come. But, even in this interview, we are constantly attended by looming death. Discussion of his plans for next year hit a wall.

“I can’t even tell you if I am in the next series,” he says. “I am completely in the dark – like every actor in the show. That’s a good thing. I don’t like knowing too much. And this year it gets really creative. There are some big shocks for people that they won’t expect. And I have to keep schtum about that.”

That must be tricky at times. When drinking pints with friends, he must have to bite his tongue if conversation moves to the series.

"It's the same with anything you do," Harington says. "You don't want to give away things with Spooks either. I don't want to frustrate an avid fan base. We have to be careful. I am used to that now."

War Horse veteran

Harington wasn't plucked from total obscurity when Games of Thrones started. A graduate of the Central School of Speech and Drama, he had already had a significant part in the RSC's version of War Horse. He could also brandish a flamboyant theatrical forename. Did his mother really call him "Kit" in tribute to the 16th-century playwright Christopher "Kit" Marlowe?

“That is partially true,” he says. “My mum liked the name ‘Kit’ and she needed a name. But mum and dad were married by a priest called Kit. So it’s a mixture of those two things.”

Harington admits that, like so many actors, he was “a bit of a show-off” as a kid. He liked to pretend, but couldn’t quite believe people would pay him to do that for a living.

Do the sums and you will conclude that he really hasn't had much time to be unemployed. He left drama school in 2008. He played in War Horse. Game of Thrones began shooting in 2010. Still, nobody can have guessed that the series would take off as it has.

“No, nobody was prepared for that,” he says. “And it was a slower start than people remember. The first series did well. The second series did better and the third series became a global phenomenon. That’s an interesting place to find yourself.”

It is indeed. He’s become a hairy sex symbol. He appears as memes. He even got to be interviewed by the less violent Jon Snow who presents the Channel 4 news. How has he coped?

“I don’t look at anything online about myself if I can help it.”

Is that possible?

“Yes, I pretty much can,” he says. “You could go totally mad if you looked at it too much. Like most actors, I like a bit of attention. But this has given me as much attention as I could want. I have achieved what I was looking for.”

A nice way to be.