Charlie Higson knew he was on the right track with The Enemy, his first venture into horror writing for teenagers, when his youngest son Sidney burst into his bedroom in the middle of the night, utterly terrified.

Set in contemporary London, the story features adults afflicted with a disease that turns them into rotting, stinking zombies, leaving the children to fend for themselves. It opens with a group of kids holed up in the Waitrose on Holloway Road – there’s a rival gang in the nearby Morrisons – sending out scavenger parties to supplement their dwindling supplies. There are acres of blood, pus and boils, and eye-wateringly violent fight scenes. And there’s death, lots of it, with the children constantly offing the grown-ups, and occasionally getting whacked themselves.

“There isn’t a set of rules about how scary you can make it,” says Higson, looking characteristically nice and respectable in his north London home (just down the road from the Waitrose). “So I used my youngest boy as a guinea pig. He was just 10, or maybe even nine, so he was a bit young. But I thought ‘I’ll see how scared he gets.’ ”

Higson read The Enemy to Sidney as a bedtime story, chapter by chapter as he wrote it. “And it was quite clear that he wasn’t getting scared at all. He was really enjoying it, and was saying ‘I love a bit of gore, but it’s not scary’ ... Modern kids have been exposed to so much more. They watch all these DVDs they’re not supposed to, they look at stuff online particularly, and certainly when it comes to gore they’ve seen it all.” So Higson responded by “pushing it, making it grimmer and more violent and nastier, with more children getting killed and eaten”.

Eventually, he recalls, they were about halfway into the book and he’d gone to sleep, “defeated again”. But then, “at about four in the morning, there was a hammering on the door and Sidney came bursting in, floods of tears, shaking, sweaty, pyjamas stuck to his body, he’d had this really awful nightmare based on the book, and I thought ‘Woohoo!’ ”

The series now runs to six books and has been a huge hit. It is Higson’s second succesful series for young adults, after he was unexpectedly approached to give young James Bond a try, 12 years ago. At the time, he was the author of four thrillers for adults: King of the Ants centres on a drifter hired as a killer, Getting Rid of Mr Kitchen a man trying to dispose of the body of the buyer of his car, whom he’s killed. “They’re very dark and nasty, you wouldn’t have thought the writer of those was the ideal choice for a children’s writer.”

Higson was also one of the creators, writers and actors of The Fast Show, and is still known today for his turn as Ralph, lord of the manor, wistfully in love with his estate worker Ted. He dreamed up the Loadsamoney character (“Look at my wad”) for Harry Enfield, with his university friend and fellow writer and actor Paul Whitehouse; and he’d spent six years as the lead singer of “scratchy white funk” band the Higsons, touring Europe and America.

So he was indeed a strange choice to further the adventures of a teenage Bond. “But actually that was one of the reasons they wanted me, they didn’t want the Bond books to be the Famous Five. They wanted them to have that dark, slightly twisted edge which the Fleming books have”.

Higson had never written for children, although he’d written stories since he was a child (fantasy and science fiction as a teenager, “arty student wank” at university, and so on). So he went back to Fleming and reread all the Bond books, collecting as many details about 007’s childhood as he could (which is not much, apart from an obituary penned by M in You Only Live Twice). Then he considered the elements that make up the best Bond stories and tried to apply them to children’s fiction.

“It was quite tricky working out how they could get in those classic elements that make Bond Bond: he’s a womaniser, he drinks and smokes heavily, he kills people and drives fast cars. They’re things you can’t have children doing.”

Higson also began road-testing the market-research technique he’d later use for The Enemy. As his first young Bond novel, Silverfin, began to take shape, he read a chapter a night to his oldest son, then 10, now 22. Again “the main thing was the books got a lot more violent and more people got killed”.

He recalls an early meeting with his publisher, when they said: “‘Does it have to be quite so violent?’ And I said, ‘It’s James Bond. If you’re going to do it, you’ve got to do it properly. Even a 12-year-old boy has got certain expectations of what you’ve got to have in a James Bond story.’ So they allowed me to do it.”

Silverfin, which sees the young James at Eton, features some truly gruesome scenes involving eels, as well as plenty of hair-raising escapes from tight corners. James learns to drive, learns to fight dirty, learns to stand up for himself. It was an instant success, not least because Higson was so clearly having a whale of a time writing it. “The scent and smoke and sweat of a casino are nauseating at three in the morning,” writes Fleming, as Casino Royale opens. At Eton “the smell and noise and confusion of a hallway full of schoolboys can be quite awful at twenty past seven in the morning”.

“Publishers are always worried that they’re going to get a backlash from parents or teachers or librarians, but we didn’t get any at all, because boys liked reading them. That’s all anybody wanted – books boys would read.” He went on to write four more, until he felt he needed to “write something that was entirely my own”. Young Bond, he says, “made me a children’s author. I was given a new career at my late stage in life which was rather nice. But I didn’t create James Bond.”

A horror fan since his teens, Higson wanted to try his hand at something scary. “Horror is a good genre for kids because you can talk about very adult things, but on a fantasy level. At some stage they are going to have to deal with death and disease and change, but they’re not going to have to deal with zombies.” And as for nightmares, “kids should have nightmares, they should be scared of things”. Remembering his own, weeping child in the middle of the night, he says: “It’s a safe nightmare, he knows awful things can happen to him, but if children can have nightmares which upset them on that level, they can learn how to cope with things, and learn how to understand what fear is and how to deal with it.”

So Higson set out to write something with “the same kick I got as an 18-year-old in the 70s watching really nasty horror films like The Texas Chainsaw Massacre. I wanted to give younger kids that. And the amazing thing is you can do what you like in a book. You have politicians saying ‘our kids shouldn’t be playing these violent computer games or watching these DVDs, they should be reading a nice book’, well, they obviously haven’t read much modern children’s literature.” So he avoided sex, and, mostly, swearing, “but violence doesn’t seem to be a problem at all, particularly fantasy violence, because it’s essentially zombies they’re fighting”.

Higson is currently writing the seventh and final book in the series, wrapping things up with a huge battle between the children and the “sickos”. It’s tricky, though, to fit in work on a 110,000-word novel with everything else he has going on. He’s recently adapted Norman Hunter’s funny, charming Professor Branestawm children’s books, to be shown on the BBC this Christmas, starring Harry Hill (Higson makes an appearance as the mayor, standing in for a poorly Brian Blessed). He’s also writing a 10-part adaptation of Jekyll and Hyde for ITV, airing next autumn, which will move the story to the 1930s, following Dr Jekyll’s grandson. There’s a feature film in development of one of David Walliams’s bestselling children’s books, and Higson also wishes he had time to write some more adult novels: he has an idea for a fantasy series that he initially wrote as a teenager. Most of all, would like to set up and produce a sketch show with new talent.

But first there is the last part of the Enemy series to finish, a project he describes as a “sort of antithesis to Lord of the Flies”, speculating that William Golding “really didn’t like children”, was scared of them en masse, and believed “if you leave children to their own devices they will become savages. I think the opposite. So that was the message I was trying to put in the books, the enemy is us, the adults, because we’re all told teenagers are terrifying, and if you go out you’ll be mobbed by gangs of teenagers who will try to steal your liver. But it’s the other way round. We’re a lot more of a threat to them than they are to us.”