As I walk round my local park every morning, I see my son slay an entire Roman legion with a sword, track rabbits with a wolf and race against time to decode a complex computer virus invented by a fiendish villain bent on destroying every trace of human life. In reality, the sword is a stick, the wolf a dog and the computer virus a last-minute piece of Maths homework. But to a boy between three and thirteen, these are all an essential part of being themselves. The pity is that to be a boy these days is to be born under a cloud. Natural exuberance is frowned on or even medicated with Ritalin; children are kept indoors instead of being allowed to run free.

The secret life of boys is, however, suddenly being given much more support this summer. On the one hand we have the film of Anthony Horowitz’s Stormbreaker coming to our screens, complete with death-defying car-chases, jaw-dropping gadgets and enough adrenaline to boot Bond into a bin liner; on the other, the old-fashioned pleasures described in Conn and Hal Iggulden's best-selling Dangerous Book for Boys reassert traditional past-times such as making a tree house, skin a rabbit or peel a thistle.

“I don’t think the imaginative world of boys has changed as perhaps girls’ has,” Anthony Horowitz says. “There’s something that is just pure, abstract Boy, which hasn’t changed since the 19th century. They still like violence, slapstick humour, gadgets, and Alex Rider very much plays on that. I deliberately don’t use slang or refer to fashionable clothes because those are so transient. I never set out to target boys, I just wrote for the boy in me.”

Despite the easy allure of computers and films, books are at the heart of the secret life of boys. Horowitz, like Philip Pullman, JK Rowling, Eoin Colfer, Terry Pratchett and Michelle Paver is popular with both sexes, but he is one of an increasingly rare breed of children’s writer who creates heroes without heroines to support or match them. This, I think, is significant. The feminist revolution has expanded the imagination and ambition of girls largely by invading the kinds of narrative that used to be reserved for boys, and boys resent it.

Horowitz’s Alex Rider gets boys back to their essential daydreams. Alex may not want to be a spy or a saviour, but he knows how to do all kinds of cool stuff, from martial arts to speaking three foreign languages. Unlike Andy McNabb’s deadly serious heroes, his adventures always have a touch of comedy or absurdity in them – as when he breaks out of a tank with a killer jellyfish by squeezing zit-cream on the metal frame.

“I did dream of being a spy, and even went as far as building radio receivers out of matchboxes when I was 9 or 10,” Horowitz says. “What I’m against is wrapping children in cotton wool. Modern life is squeezing danger out of children’s lives, because parents fear a paedophile on every street corner. Where is the spirit of Shackleton?”

Even if they are not quite as naughty as Francesca Simon’s Horrid Henry, the kind of unambiguous, confident hero celebrated by H Rider Haggard, Conan Doyle, Herge and John Buchan is a rare find in books or film. (Tolkien’s Aragorn, who never doubts his moral strength, is a very different creation to that in Peter Jackson’s Lord of the Rings.) Yet any parent who tries to ban guns will find their son biting them out of toast. Guns, swords, lavatory humour, practical jokes and dreams of glory are hard-wired into the male sex, and adults’ failure to find this endearing and funny is at the heart of why so many authors do not reach boys..

Until very recently, children’s literature portrayed a pre-lapsarian age: magic depended on not growing up, like Peter Pan. Ursula le Guin’s Wizard of Earthsea, Ged, specifically binds himself to chastity when becoming a mage, and only loses his virginity once he has also lost his magic; ditto Superman who had to give up his powers to have sex with Lois Lane. Comic book heroes may love the girl next door but Spiderman and Wolverine etc., are always prevented from doing more than kissing them; one of the most popular Playstation games for boys, The Prince of Persia, has its hero fight innumerable demons only to have his beautiful princess lose all memory of her saviour at the end. The magical ability to pass into other worlds ends soon after Will and Lyra consummate their love in His Dark Materials; my own 10 year old son was horrified at the idea they had sex, and refuses to believe it. For boys, who take on average two years longer to reach puberty, chasitity is an essential part of their fantasy life. A classic children’s novel of the 1960s such as Geoffrey Trease’s Cue For Treason or CS Lewis’s A Horse and His Boy quite often ended with the hero and heroine (often disguised as a boy) marrying each other when they grew up, and this was as satisfying as the traditional end of a fairy-tale.

Now, however, much-loved modern series such as Michelle Paver’s Chronicles of Ancient Darkness which feature a boy and a girl (Torak and Renn) are read with increasing anxiety by boys who realise that the nature of their relationship may change. Stone Age Torak is in one sense a classic boys’ own hero as he survives with little but a slate knife, a bow and a wolf – but how long before he and Renn start behaving like Adam and Eve? It’s obvious that, as Wolf matures, some kind of sex is going to happen soon – the new novel, Soul Eater, ends with some tantalising facts about wolf cubs – but boys do not want their hero and heroine to get emotionally involved. When Harry Potter succumbed, and snogged Cho Chang, then pretty Ginny Weasley, half his fan base among under-12s evaporated.

Alex Rider does have a girl friend, Sabina Pleasure, but she is not a girlfriend. Despite being gorgeous, he only kisses her once at the end of the third book before saying goodbye to her forever. Originally, the kiss was described in some detail by the author but after he read the scene to his sons, then aged 12 and 14, they reacted so strongly against it that it was cut. They felt, he said, that although James Bond had sex, they were “uncomfortable” at having a boy their own age having these feelings.

“Alex doesn’t have sex,” Horowitz says. “Sex erodes what I’m writing about, it interferes with childhood, with that total immersion of creating a world within a world.”

Our sons need this world badly, and the fact that their innocence will come to a natural end some time during their teens does not mean it should be brought to a deliberate halt. The runaway success of The Dangerous Book for Boys (which includes a sensible chapter on talking to girls) has hit a nerve precisely because the secret life of boys has retained all its essential characteristics, despite receiving very little encouragement over the past twenty years.

“I still remember the tremendous exuberance of being a boy,” Horowitz says. “It has an almost abstract quality that you can’t create by artificial means.; I think a lot of authors who’ve fallen flat on their faces trying to write books for boys because they think there’s big money in it do so because you can’t reinvent it if you’ve lost it. The most horrifying thing I heard at a school was that a child was allowed to read my books for pleasure because they had passed an exam.”

Boys today no longer want to join the Boy Scouts but the Just William kind still wants to around build dens in woods, dam rivers or just race through the streets on their bicycles as Alex Rider does in Stormbreaker’s most thrilling chase sequence. They want danger. The fact that many parents are too busy, or too frightened, to allow this is what has done most to push them into the kind of fantasy in which the only action is the pressing of thumbs on console buttons – and where heroes are resolutely bold, brave and living in a world of their own.