“when I thought up the first Alex Rider book, I didn’t want to have gadgets at all. I was afraid that having someone in a white coat giving Alex secret weapons might be too similar to the man called Q who appears in the James Bond films (you may have noticed, by the way, if you’ve read Scorpia, that Mrs Jones has a cat called Q). I was persuaded to change my mind after a series of school visits. Everyone I spoke to wanted gadgets. More than that – they expected gadgets. It’s hard now to imagine the books without them.

Secret gadgets actually began a long time before James Bond. During the Second World War there was a wonderful organization called the Special Operations Executive – or SOE – which was famously told by Winston Churchill to “set Europe ablaze”, using sabotage and guerrilla warfare behind the enemy lines. They had a special section that came up with all sorts of exotic weapons to use in the fight against the Germans. I found out about them when I was writing the television series, Foyle’s War…I also discovered that Ian Fleming, the author of James Bond, worked for the SOE himself, so that was where he must have got some of his ideas.

My favourite SOE gadgets – and remember, these all existed for real – included a special sort of powder that could make a car grind to a halt, miniature submarines and “sticky” bombs which were hopelessly dangerous. The idea was that you would attach them to the underside of a tank and then somehow roll away before you were crushed or blown up. The SOE put bombs inside fake rats. Their agents were instructed to leave them in German factories. The Germans would find them and get rid of them by shovelling them into the furnaces – and in doing so would blow themselves to smithereens.

The SOE also hid bombs inside camel dung. These would be left on the sand, and military vehicles would drive over them without realizing they were in fact miniature mines. They even invented an extra-strong itching powder which they planned to put in the German laundry. I wonder if anyone would believe such a thing if it appeared in an Alex Rider book?

I still find creating the gadgets quite a challenging part of the stories. To start with, they always have to be concealed in items that you would expect to find in the pockets of an average fourteen-year-old and, when you really think about it, that rather narrows the field.

What’s in your pocket right now? In the first eight books in the series, Alex has carried a key-ring, mosquito repellent, bubble gum, a drinking straw, a packet of chewing gum, three coins, a gel ink pen, a Harry Potter book, a pocket calculator, a yoyo, a mobile phone, a tube of zit cream, a rubber, an inhaler, an iPod, a postcard and a Game Boy. I wonder how many of the books you were able to identify from that list … and what did each gadget do? You’ll find the answers at the end.

The gadgets have to be realistic. It seems to me that the gadgets in the James Bond films got sillier and sillier until you ended up with the X-ray glasses in Tomorrow Never Dies and the invisible car in Die Another Day. This is only my view, but surely everyone knows that this sort of technology is not possible yet – and if you don’t believe the glasses and the car, how can you believe anything else in the films?

The next problem is that the gadgets have to be non-lethal. You may be surprised to learn that my publishers get very uptight about Alex killing anyone … and I’ve written about this aspect of my writing life at the back of Scorpia. It’s one of the reasons why Alex never, or very rarely, carries a gun. In some of the books, Smithers does mention very destructive weapons such as the model seven mobile phone (Skeleton Key) that will blow off your hand unless you hold it upside down when you dial. “Why can’t I have that?” Alex asks. “Mr Blunt has forbidden it,” Smithers replies. The gadgets have to be useful and fun but they can’t be too bloody.

Since I’ve mentioned Smithers, let me tell you a bit about him. He was named after a minor character who appears in the James Bond book, Goldfinger and I made sure that from the start he was as different as possible from Q. In Skeleton Key, and again in Crocodile Tears, we meet him in his office which is itself full of bizarre devices including a lift concealed in a filing cabinet. One day I would like Alex to visit him at home. I imagine he lives alone in a small, terraced house which will also be packed with secret weapons – from the gnomes on the front lawn to the satellite dish on the roof.

Smithers is deliberately old-fashioned and doesn’t seem to belong to the cold, hard-edged world of MI6. He is the only person who really cares about Alex. I like the section in Eagle Strike when he disobeys orders and gives Alex the Cannondale Bad Boy bike … which is also one of my favourite gadgets, particularly the ejector seat saddle. He was inspired by a man called Harry Thompson, who taught me English when I was twelve years old and who was bald and fat and wore three-piece suits. He was the only decent teacher in my truly horrible school.

What’s more, I know something about Smithers that nobody else does. There’s one gadget that’s been on display in all eight Alex books but which has never been revealed. It’ll finally show up in the ninth Alex book.

But the real difficulty when it comes to creating gadgets is how to use them. They have to save Alex’s life but at the same time they have to surprise the reader. For example, suppose Smithers gave Alex a can of deodorant that concealed a spray that put cobras to sleep. And then imagine that, ten chapters later, Alex found himself in a room with a dozen deadly cobras. No problem! He whips out the can, gives a quick squirt and he’s fine. The trouble is, I think people would feel cheated reading that. It’s too obvious. It would almost be as if Smithers knew exactly what was going to happen.

I try to use the gadgets when they’re least expected. Perhaps the best example of this (I hope) is the last-but-one chapter of CrocodileTears and the death of Desmond McCain. It’s great that Alex has a few weapons up his sleeve, but I like him to use a bit of intelligence too.

Finally, one question I’m asked all the time: which is my favourite gadget? I rather like some of the more bizarre inventions which Smithers mentions but which don’t ever get used … the poncho that turns into a parachute, for example (Skeleton Key) … or the Buddha hand grenade in Snakehead (“Anyone within ten metres can say their prayers.”). But my real favourite has to be the bubble gum which Smithers gives Alex in Skeleton Key. When you chew it, it becomes an explosive. But what makes me smile is the name – BUBBLE 0-7.

Actually, it was a good decision to include the gadgets. In fact, I can’t think why I was so worried about them in the first place.”

Answers to gadgets quiz

The Michael Owen keyring (Skeleton Key) was a delayed-action stun grenade.
The mosquito repellent (Ark Angel) attracted insects … in their thousands.
The bubble gum (Skeleton Key) turned into an explosive after it was chewed.
The drinking straw (in Scorpia) contained a knock-out dart and worked like a blowgun.
The three coins (Snakehead) were also explosives with the detonators hidden in the packet of chewing gum.
The gel ink pen (Crocodile Tears) contained gelignite.
The Harry Potter book (Point Blanc) fired a tranquilising dart from its hidden chamber – it was HarryPotter and the Chamber of Secrets.
In Crocodile Tears, Alex was given a pocket calculator that contained a communications system.
The yo-yo (Stormbreaker) yielded thirty metres of advanced nylon cord for climbing.
The mobile phone (Skeleton Key) fired an anaesthetic dart.
The zit cream (Stormbreaker) ate through metal.
The inhaler blew up, and the iPod used microwaves to become a listening device – both were given to Alex in Ark Angel.
The postcard in Crocodile Tears contained a hidden guidance system.
And the Game Boy, which appeared in Stormbreaker had many functions depending on which cartridges were inserted. Alex used it as a smoke bomb, a communications device and a bug finder.

Anthony Horowitz