I’m sitting in a small green room, tucked away behind the Queen Elizabeth Hall at London’s Southbank Centre. I am in an area of restricted access, safe behind a labyrinth of small, wooden doors. In here everything is quiet. The air is heavy with anticipation. Yet outside, there are massive crowds swarming the Southbank Centre. Earlier, when I was out among those very crowds, I felt the buzz and the energy of all the people present. At the Imagine Children’s Book Festival there’s always something exciting around every corner. The best authors come here to share their art with the reading community. Today, in this small room, I’m here to talk to the best of them all: Anthony Horowitz.

As an immense fan, I am humbled by this opportunity. I have read many of Mr Horowitz’s books and have so many questions that I wish to ask. From the way his books are composed, I can guess he will be an intelligent man, with a strict demeanour. Even as he enters, I know I got one thing right. The man is very intelligent. You can tell from the moment you look at him. His eyes sparkle with a hidden sense of humour. There is a sprightly spring in his step. He is dressed in a crisp, black suit and a white shirt. We sit down, and I try in vain to hide my star-struckedness from my life-long hero. Determined to make the most out of my time and curiosity, I begin.

Alex Rider is one of your most famous series. Of course, most recently we saw the return of Yassen Gregorovitch in Russian Roulette, which is a prequel to the Alex Rider series proper. I have noticed there are many similarities between Yassen and Alex: they’re both headstrong, intelligent, confident and have suffered from the deaths of their parents. So I was wondering what made you so interested in pursuing his past and were these similarities intended?

It’s a very good observation that they’re similar. That was one of the things that interested me. If you take two people and they are similar in so many ways – they’re young, they’re lost and they’ve suffered personal misfortune – what are the choices they make that make them either good or bad? Why is it that Alex turns up as a hero but Yassen turns up as a villain? I thought that was a very interesting area to explore, particularly as the main reason Yassen goes bad is all down to Alex’s father who he meets in the course of Russian Roulette. It was a fantastic journey for me to write about. Also, it’s not exactly as a prequel as it brings Yassen and the series full circle. The series began with Stormbreaker where the two of them meet in the climax with the helicopter and the dead body of the bad guy in between them and this book goes full circle and returns to that moment and really completes the series in a satisfying way.

Your Alex Rider books saw Alex begin as a fun-loving, stylish and charming kid but turn into a darker, more mature and scarred man in a way. What prompted you to make this change and was it planned from the beginning? Also, do you think that Alex will ever recover from the events of Scorpia Rising?

I can’t tell you how happy I am you’ve asked that because one of the interesting things about the Alex Rider series for me was that the more I wrote about him, the more adventures he had, the more I found myself compelled to take this darker edge. This kid is 14 years old. He’s now been involved in all these deaths; all these different mad people trying to do horrible things to the world. He’s had a man commit suicide in front of his eyes by shooting his own brains out. If you were to think of him as a real character even a little bit, there must be a change to him. He must become damaged by all that’s happened. As I went on I was constantly having to fight this feeling that he should become a depressed character. But kids don’t want to read about characters that become depressed…

There is in the back of my head one little thought I would like to do. I would like to write a book about Alex Rider aged 29 or 30. I’d love to see what became of him but I can tell you the first chapter will have him rolling out of bed in a disgusting room. There’s going to be a cigarette in an ashtray. There’s going to be an empty bottle or something on the ground. He will be seriously damaged by all that’s happened. In that book I will try to work out how he can have a normal, happy life.

In one of the Diamond Brothers books the Brothers are in collaboration with MI6, which is headed by Alan Blunt. So are Alex Rider and Diamond Brothers set in the same universe? If so, what would you think of a crossover?

I can’t remember putting Alan Blunt into a Diamond Brothers book but if I did it would be a bit naughty ‘cause that’s going too far! But I do like the idea that all these characters – Alex, the Brothers and even Matt Freeman – come from the same universe which is inside my head. They’ve all existed at some time in my brain so why shouldn’t they meet? I certainly do remember putting a character called Jeff Stryker, who owns a car manufacturing plant, on the Southbank. I think he turns up in both Diamond Brothers and Alex Rider.

Which book out of the Alex Rider series was the one that you enjoyed writing most?

Well, I enjoy all my writing equally. Every writer enjoys writing every book and the one after it. I get very passionate about writing and I love doing it otherwise I wouldn’t be able to do it. I guess Stormbreaker was probably the most satisfying because it changed my career. I went from selling 10 to 15 thousand copies a year to selling 40, 50 thousand. It was a huge breakthrough for me. So I have a fondness for that book. It’s not my favourite Alex Rider though; if I was to choose the one I most enjoyed writing it would probably be Scorpia. I loved Julia Rothman (the Villain), I loved the plot. I loved creating the bad guys, Scorpia. Snakehead had one of my favourite chapters in the series where Alex was going to be cut up and his organs were going to be harvested. I found that so compelling, I don’t know why. Poor kid; it must be terrifying! No wonder he’s damaged.

I was wondering who or what inspired Alex. Are there any people you know or knew that shared character traits with characters from the books?

Well, yes. Clearly he came out of James Bond. That was where he began. The idea began with the thought that wouldn’t it be great if James Bond was a teenager? Having had that thought the secret was to make him as different from Bond as possible and I based him on lots of people. Mainly it was on a son of a friend of mine; a boy called Alex. He came to lunch around the time I was thinking of the book. He spoke French because his father was French (his father is one of my best friends). He was quite a physical boy. He did Taekwondo and various sports so I used bits of him for Alex.

What appealed to you to introduce a new cover art of the Alex Rider series? Does it ever make you nostalgic?

That’s not really my decision to be honest. Although I do think that covers are terribly important and I think we’ve done extremely well with Alex. The cover series we just finished with, which has been around for at least five years, set a new standard in children’s book covers. They were so wonderfully abstract and vibrant, visible and mature. I think the most important thing was that they looked adult. I don’t think children’s book covers that look childish are anything I like. Within the world of publishing if you don’t rejacket or redesign the covers they’re going to look a bit old. If you’re looking for a new audience then a new set of covers is good because kids are getting older and every year new kids will come into the age range of my books. It was a publisher’s decision though. You do realize I’m seeing these new editions for the first time with you? Quite exciting!

You’ve been writing for a long time now, so I was wondering if the Diamond Brothers series could get a new book?

There is one more book to come, The Radius of the Lost Shark, which I’ve been talking about writing for years and years, and which I set in Australia, but I’ve got about six books at the moment before I can write the Diamond Brothers book. It may be one to read to your grandchildren! I’ve finished Foyle’s War. Alex Rider is complete. So there is just one more Diamond Brothers book to close the series then I can just quietly become senile and die, I suppose.

Some of the earlier books you wrote in your career were the Groosham Grange series. I really enjoyed them because the storyline really appealed to me. I found the first book especially dark because of the scary witchcraft plotline and that crazy, genuinely unexpected twist in the end. You had a sequel to it which expanded the story beautifully. Is there any chance that you would be adding further to that series in the future?

I was going to do a third book in that series and I would have liked to have done it because it was a great character and I would have liked to do a whole lot of things there. Unfortunately for me, as soon as I wrote Return to Groosham Grange somebody else had the same idea about a school that teaches magic and a child that is a wizard, and they did rather well with it and sold quite a lot of copies… It put me off doing any stories about that particular world.

Your recent novels have been for older readers, such as the Sherlock Holmes novels and a Bond novel which is due to come out at the end of this year. Since you’ve written the Diamond Brothers which is also a mystery series, what changes when writing for adults rather than kids and do you find any challenges when writing books for older audiences?

Very good question. A very difficult one to answer. I think that there aren’t that many differences, curiously. There are more similarities than differences really. I think that in both, narrative is important. The thrust, the drive of the book. That’s where I begin when I’m writing; basically with story and moving, getting people to motor through. Cliffhanger endings! Surprises, twists, and things you can’t see coming! If you read Moriarty, you’ll see that the ending of that is such a shock. I love that idea. It’s almost childlike that when you get to the ending of the book you’ll say, “What?! You can’t do that! Oh my God! What’s going on here?!” You then throw the book away and wish you hadn’t read it, or then re-read it and say how clever it was. So there aren’t that many differences.

They are possibly linguistically different. My adult books may be a little bit more challenging. My Sherlock Holmes books are written in a 19th century style. I’ve just started writing a new book called Magpie Murders. In terms of the amount of detail you have to absorb it’s probably too much for a very young reader. There are so many characters, so many plot points, the clues to absorb! It was interesting writing the Bond novels; I kept having to stop myself and say, “Oh my god, I’m writing all this stuff that I’d never put into an Alex Rider book.” Yet that was the one difference there had to be.

On a final, more personal note, many authors have a personal space which is customized or a special place where they like to write. What kind of a set-up to do you have?

I used to have a lovely studio in my garden where I worked but unfortunately my wife sold the garden. Actually she sold everything. Now I live in Central London and I work in a very long office. It looks out onto the Old Bailey and St Paul’s. It’s purely work dedicated and I like to look everywhere around the room and be inspired. There’s a spider sitting on one shelf in a big glass case that’s out of Eagle Strike. There’s a rocket there which is sort of Ark Angel and it’s also sort of James Bond. Things I look on in there inspire me. But by and large I’ll work anywhere; I’ll work in a café, or if I wasn’t talking to you I’d be working in this room now. I’ll just work wherever and when I’m working I’ll absorb myself into the work so much I’ll barely notice where I am.