We talked to writer Jack Thorne about adapting a much-loved book, trees, and the nature of romance…

Warning: this interview contains spoilers for Let The Right One In.

Jack Thorne knows all about the pain of being a teenager.

Lets start at the beginning.

How did writing a stage adaptation of Let The Right One In come about?

But I think John can do magic things on stage.

I love the book, by the way.

You dont want to be the one who does the terrible thing that screws up the thing you love.

It must be harder when you love something.

I think the worst job in the world at the moment is probably JJ Abrams job.

I mean, he can think as long as its not as bad as Attack of the Clones…

Anyway, lets get back on topic.

How did you decide what to cut and what to keep in?

That was the starting point, and then it was just going, okay, whats their story?

And everyones got their own Oskar, do you know what I mean?

The interesting thing about the American film is that Oskar is quite sexualised.

I think your Oskar is maybe a bit more sympathetic than some of the others.

But hes still you know, hes not perfect.

And the bullying scenes are quite severe when you see them on stage, theyre different.

Theres probably a bit more bullying.

Its really interesting, what that means.

I think its very hard being young.

We were never told what to do, we just had to tell the story.

But there was never any commercial pressure put on us.

Another thing about this adaptation is that its set in the 80s, right?

Why make it a period piece rather than bring it up to date?

Well, when you bring something up to date you get into all sorts of trouble.

The mobile phone thing is very interesting, in terms of what it does to horror, in particular.

But the other reason is that it felt like it was a story about the 80s.

The stage design is really striking.

How did it feel when you first saw it?

I think its amazing.

Christine Jones is the designer, and shes amazing.

That forest in Dundee, it was still growing.

Like, I want some trees for a play, Ill take that one?

I think she literally did do that.

They showed her the trees they were felling, and she went round and chose the trees she wanted.

You know what, I said to John, why dont I write this in the gym?

Its brilliant, I think, but no, I was a total wimp about it.

I would not have tried to do it.

Lets talk about the casting.

Were you involved in casting Martin Quinn and Rebecca Benson?

Were they what youd imagined for your version of Oskar and Eli?

There was just something about the way Martin held himself that made me think, oh, its Oskar.

His shoulders have got bigger since then but hes still got that sense about him.

Were up to about 90 performances now and each one has got better and better and better.

The first time you see her, standing on top of the climbing frame, its so creepy.

And just the way that she drinks blood?

She does something with her back.

Speaking of movement, there are dance sequences throughout.

Was that something you wanted to include?

What do you think those add?

I think it makes it feel more like a fairy story.

I think as a play, mood is very important.

Dance allows you to understand Oskar a bit better, I think.

My favourite scene is Oskar and Eli post-sweetshop, when theyre running around with the bananas.

Obviously I didnt write a word of that but I love it.

I look forward to it every time I see it.

How many times have you seen it?

Lots and lots and lots.

Why do you think people keep coming back to this story in one way or another?

I think Lindqvist did something completely new with vampires.

I love genre and to do something new with that is hard and brilliant.

Have you read his other books?

Yeah, yeah, yeah.

Brilliant, isnt he?

And hes a very interesting man, too.

I got to hang out with him a bit and hes very cool.

And totally at ease with the fact that people have taken his story and done interesting things with it.

I didnt meet him until after wed done the play, but I was full of questions.

Like the Oskar/Hakan thing, is Oskar going to grow up to be Hakan?

Because in the book, hes clearly not, but in the film, theres a possibility.

I think thats how she feels with Oskar.

Thats even more depressing though, that she would go into it thinking that?

When as an adult you know it probably wont work out like that?

Maybe Im just old and miserable.

You dont know that.

Or maybe she turns him into a vampire.

There are many different ways this could work out.

And I think thats how she feels.

Jack Thorne, thank you very much!

Let The Right One In is at the Apollo Theatre in London until 27 September 2014.