King of tall tales: Why children's author Philip Ardagh's is literature's biggest joker

When I meet Philip Ardagh for coffee in late October, the winner of this year's Roald Dahl Funny Prize has not yet been announced. But Ardagh is sure he knows which of the six shortlisted books will win – and it's not his own.

The award was created last year by the then-Children's Laureate Michael Rosen; funny books, said Rosen, are not taken seriously – neither receiving the review coverage "serious" books do nor being considered for the mainstream prizes – so a new award was needed, one whose overriding selection criterion was whether the book submitted made the judges laugh. It would (so was the hope) draw attention to fine comic writers who might otherwise be overlooked.

Ardagh, though, is hardly at risk of being overlooked. (And not only because he's a pretty conspicuous two metres tall.) He has written about 100 books, and has had considerable popular success with them in recent years; his Eddie Dickens series has been translated into 34 languages; and when Paul McCartney decided he wanted to write a children's book, it was Ardagh who was ' suggested as collaborator. This is no languishing tyro gasping for a first shot of publicity.

Ardagh began to write, he says, "even before I could write. Because for me writing is two things, one of which is the ideas, wanting to get the stories out, but it was also from a very early age the physical process of making marks on paper. My father was given some old diaries, and they looked just like books, and I used to do squiggles in them, and draw pictures, and eventually I was doing words, and sentences..."

Having completed what was then the country's only copywriting course, Ardagh worked in an advertising agency, but after a long day's writing in the office trying to sell products, the last thing he felt like doing when he got home was sitting down to write stories; so in the early 1980s he quit advertising and took a job as a hospital cleaner, writing in the day and cleaning at night. (The hospital didn't have uniforms big enough to fit him.) There then followed work as a highly unqualified library assistant, and many years of writing non-fiction, usually commissioned for a fixed fee and no royalty, which was not enough to establish a reputation, still less earn a good living. And then Eddie Dickens happened.

It began as a series of letters written to Ardagh's nephew Ben at boarding school – Ardagh was sympathetic, having been at boarding school himself – in which he described a surreal pseudo-Victorian world where young Eddie Dickens' parents turn yellow, get a bit crinkly round the edges and start smelling of hot-water bottles, so the unlucky boy is dispatched to stay with his mad relatives at Awful End. Untroubled by thoughts of a wider readership, by constraints of what a publisher might expect, Ardagh's writing was suddenly freer, more spontaneous, and because he was writing to someone he knew, he could break out to address his reader whenever he felt like it. The story was wild and engaging, the narrative voice attractively subversive, and before long Ben was sharing it with his friends, their housemaster gathering the boys together to read each new instalment.

The first Eddie Dickens book, Awful End, was eventually published in 2000, and readers loved it. Given that this is a book that was not plotted with a clear story arc, not drafted and redrafted, they can hardly have expected great success, but when Faber reached its 18th reprint, they began to suspect they were on to a good thing. The series introduced a selection of eccentric characters – though "eccentric" doesn't seem quite enough to describe Marjorie the hollow cow, Even Madder Aunt Maud, Malcolm the stuffed stoat or the narcoleptic New York hypnotist – plus some tight plotting and, perhaps most importantly, that highly original narrative voice, which speaks directly to the readers, frequently interrupting the action for a comment aside or a grumble.

(When we get to talking about the illustrations by the "fantastic" David Roberts, Ardagh at one point breaks from the thread of his story to speak directly into the recorder: "David, if you are reading this..." The effect is not unlike reading an Ardagh narrator, suddenly completely over-present when you least expect him, editorialising himself.)

That authorial voice, Ardagh acknowledges, is something you either love or hate: "If you don't like how I get in the way of the story, I get in the way of the story." But rather that, he says, than something inoffensive and "slightly bland". He takes great pleasure in quoting a reviewer who found his tone almost unbearably irritating.

Apart from the impressive height, the other fact compulsory to mention when describing the public face of Philip Ardagh is his very impressive beard. (Presumably the beard stays on in private, too.) When asked for a general comment on Ardagh's appeal, Rosen says: "Philip Ardagh is one of the most bearded writers of all time, out-bearding Karl Marx and Charles Darwin. What's more, his jokes are better than theirs. Much better."

It is as Grubtown resident Beardy Ardagh that he narrates his new series, the delightfully daft Grubtown Tales. In Grubtown, Beardy Ardagh can be more than just a narrator; as a town resident, he can justify his involvement in the action, unlike in the Eddie Dickens books, where he may have interfered in the storytelling but could never be part of the action, "because I wasn't alive in Victorian times". (Which sounds sensible when you're sitting having a serious conversation, but when you come to transcribe the tape and stop to think about it, is, of course, nonsense.)

Unlike many children's books, where the child characters are given an unrealistic degree of agency (a closed environment such as boarding school, or the parents away, or the child orphaned), Ardagh denies his fictional children the chance to manage their own destiny: "We live in an adult world, and adults are often as clueless as children, if not more so – and they have the power." So while Grubtown's two main characters are children – we argue about which one is actually the main character, but since I'm the one writing this piece, I'm going to say it's the boy called Mango Claptrap – most of the population are adults.

There's the mayor, Flabby Gomez (in a town with "one man, one vote", Gomez is that man, and he always votes for himself); there's Kumquat "Grabby" Hanson, who doubles as chief of police and town thief, so frequently arrests himself (the town's clear-up rate is impressively high); and the Foxes, a family characterised by a militant hatred of ducks. (If you happen to find yourself passing the shop called "Kill All Ducks", that's theirs.) Though it is for younger readers than most of Ardagh's fare, Grubtown is exactly as knowing and subversive as it sounds.

With the first four titles in a new series, "Henry's House", just launched – Dinosaurs, Egyptians, Bodies and Creepy-Crawlies – there is still plenty of non-fiction in Ardagh's life, too, allowing him to enthuse about things that excite him, and to meet interesting people, such as the British Museum staff who once talked to him about hieroglyphics. On such subjects, his passion is indeed infectious; as a reader of everything and anything (shampoo bottles, cereal packets), he rhapsodises on Ed McBain so convincingly that after the interview I find myself ordering a copy. With his narratorial in-jokes, Ardagh recognises McBain's (unlikely) influence on Awful End. And beside McBain, there's Sherlock Holmes, the Moomins and John Irving; and, of course, Eddie's forebear, Charles Dickens. Dickens Sr has fingerprints all over Ardagh's books.

Ardagh is relaxed (he is extremely good company) and also clearly a highly focused professional with high demands on himself (as a hospital cleaner he "wanted to be the best hospital cleaner there was"). He jokes once, in a casual gentleman- amateur-having-a-laugh way, that if the interview recording is inaudible above the noise of the Tunbridge Wells coffee machine, I should just "make it up"; but also in jest he offers specific suggestions for what I might like to write about him (he likes the idea of "leonine"). The Ardagh persona contains both of these – at once seemingly flippant, and, he says, a control freak, a writer whose Eddie Dickens manuscript included incredibly detailed written briefs for what he wanted in every single illustration. As Roberts recalls, "He will lavish you with praise, while giving feedback on every single illustration. No detail goes unnoticed; he was always telling me off for making everyone left-handed..."

So what's next? Ardagh is a busy man, and it is hard to imagine that he has ever not been. Apart from the growing "Henry's House" series, he has several other books completed and slated for publication next year (Faber's 2010 catalogue trails Grubtown volumes 4-6); there is the big-screen adaptation of High in the Clouds, the McCartney collaboration, for which "Paul is writing the soundtrack" (related very casually, as though having a Beatle writing one's soundtrack were quite unremarkable); and there are ideas still at early-germination stage. "I have for some years been thinking of writing a book in association with Charles Dickens. Obviously he would get a smaller credit."

So back to the Roald Dahl Prize. (Ardagh has not, he says, read Dahl's The BFG; in Dahl's world of evil giants, the only giant who is benign is the beardless one, which must be hard to take if you are 6ft 7in, magnificently bearded and generally benign yourself.) On 10 November, a fortnight after our meeting, the judging panel, which includes the comedian Bill Bailey and a clutch of children's writers and illustrators, announced their 2009 winner, from a shortlist including Little Britain's David Walliams, former Children's Laureate Anne Fine (for a book Ardagh loved, and not just because it's filled with first-class beard comedy), and Andy Mulligan's Ribblestrop, Ardagh's own tip to win. He correctly predicted last year's winner, Andy Stanton, before even the longlist was announced; so he is confident in his choice this year – "When I read Ribblestrop last year, I thought, 'This book must win the second'; I thought it was wonderful..." Besides, "They always give it to Andys. If Andy Williams ever writes a children's book he'll win the Funny Prize."

Well, not this year. This year's winner was Grubtown Tales: Stinking Rich and Just Plain Stinky, by Philip Ardagh. Chair of judges Rosen commented, "Philip Ardagh creates a world of craziness with a prose full of asides, mutterings and allusions to the writing itself. He deserves all he gets. And a shave."

The extract

Grubtown Tales: Stinking Rich and Just Plain Stinky (By Philip Ardagh Faber £4.99)

'...Meet the Repulsive Mr Org. Manual Org was repulsive. How repulsive? I'll tell you how repulsive Manual Org was... He once entered a competition to find the "Most Repulsive Person in the Area at the Time" and he was disqualified... for being too repulsive. Would I lie to you? (Except for money)'