If you took a poll now to find out who people think is the greatest living children's author, the result would be tediously predictable. Potter trumps all. But what would happen if you brought criteria other than immediate popularity into the picture - awarding points for originality, intelligence, clarity of style, emotional depth, and sheer range? There is not much doubt, in my mind, that the winner would be Peter Dickinson.
Many people remember him for his first children's book, The Weathermonger, set in an England that has mysteriously reverted to the Middle Ages, where magic is seen as part of everyday life and machines are treated as the work of the devil. It kicked off a trilogy, The Changes, which was dramatised for television in the Seventies.
Dickinson himself is a little weary of having that one brought up - understandably, since he has written more than 50 books since, for adults and children, across a number of genres from ancient history to science fiction. Along the way he has gathered what is probably an unequalled collection of awards, and the admiration of his peers. Philip Pullman has written that "His books carry a charge of excitement, and a restless exploration of large ideas, which I find unfailingly thrilling."
Peter Dickinson turned 75 last year. When I met him in Winchester, where he lives, he talked a fair bit about the trials of old age; his awareness that he can't churn the books out the way he once did. He struck me as not so much old as ancient, to the point of timelessness. He has an arresting appearance: very thin, with longish white hair and skin so pale it seems almost translucent, but a jaunty manner. The general effect, enhanced by a broad-brimmed black hat, is of an unusually spry Old Testament prophet.
He is an energetic talker, and although he complained that his memory was not what it had been, he can recite reams of poetry. The voice is distinctive, too: he told me that people he hasn't spoken to for 20 years will still say "Peter Dickinson!" when he phones them. "Hooting" is his own self-deprecating adjective; certainly, it has a very fruity quality, and an unselfconscious poshness you do not hear very often these days.
Dickinson himself plays down his poshness. His father's family were well-off, what he calls "Squirearchy with intellectual pretensions", and politically active. His grandfather was a Liberal MP, an early supporter of women's suffrage and a founder of the League of Nations.
But Peter's father died when he was young, leaving his mother with four sons and very little money. There was always family money to rescue them when they were in trouble, but "It's not a comfortable position. I was always very conscious of being brought up on the fringes of things, being outside things. I feel very much an outsider, I still do - not the Angry Young Man sort of outsider, but very much the person looking in."
It is interesting to compare him with Orwell, who wrote about the agonies of life at the lower end of the upper classes. Both were scholars at Eton, too, though Dickinson insists that he won "the bottom scholarship in the worst year". Dickinson himself suggested a comparison with Kipling, wandering around Simla peering in the windows of officers' clubs. Like Kipling, he came to England after an idyllic Imperial childhood: his father was a colonial civil servant, and Peter was born in Africa, "within earshot of Victoria Falls".
From Eton it was a natural progression to King's, Cambridge, where he read classics, then English. He stayed on to do research; a first was not a prerequisite in those days: "And then, purely accidentally, I got a job on Punch". The youngest member of the magazine's staff had just celebrated his 40th birthday, and it had been decided that some fresh blood was needed. The editor wrote to Dickinson's tutor, who put him forward for the job: "I was the only candidate - run over by a tram on my way to the interview, arrived covered with blood and dust."
Dickinson stayed at Punch for the next 17 years, through three editors, including the Malcolm Muggeridge era. He wrote a lot of funny verse, at which he claims to be extremely proficient, and ended up as deputy editor. In the mid-Sixties, while reviewing detective stories, he came up with an idea for one of his own: "I very much thought I was going to be 40 fairly soon and I must write something."
He settled into a routine of two pages every evening after work, but after some months lost confidence. One night he had a nightmare, and lay awake turning it into a story: this became The Weathermonger. "I wrote The Weathermonger to unblock my adult novel, which it did, successfully." The adult novel, Skin Deep (these days better known as The Glass-Sided Ants' Nest), won the Gold Dagger for crime novel of the year, as did its sequel.
Dickinson's immediate success should stand as an inspiration to every late starter, as should his astonishing subsequent productivity. He took the opportunity of a regime-change at Punch to take up fiction as a full-time career, and for the next few years wrote two books a year: an adult novel over the two winter terms and a children's novel over the summer term, spilling over into the holidays. "At times," he says, "it's been a bit of a treadmill, but it's been enormously rewarding. It's a second life. You live in your books."
The most impressive feature of Dickinson's works are their diversity. They include all-too-plausible science fiction such as Eva, set in an overpopulated near future, about a girl whose mind is transplanted into the body of a chimpanzee; realistic political thrillers such as AK, about a boy-soldier in an unnamed African state; and beautifully done historical adventures such as Tulku, set during the Boxer Rebellion. And in The Ropemaker, he ventured into what he calls "high fantasy" - by which he means, I think, fantasy set unambiguously in another universe.
Several books cross the boundaries between genres in unpredictable ways. The Blue Hawk, the story of a boy-priest who unintentionally brings down the theocracy he serves, reads like a historical yarn, apparently set in ancient Egypt or Assyria; but towards the end it becomes clear that it is in fact science fiction. This empire is not historical but futuristic, built from the wreck of our own civilisation; the gods worshipped here are some sort of star-beings.
Dickinson's latest book, The Tears of the Salamander (Macmillan, £9.99) begins as straightforward historical adventure. Convincingly set in Renaissance Italy, a world of warring princelings, it morphs seamlessly into fantasy. Alfredo, the hero, is taken to his ancestral home on the slopes of Etna, to be told that he has inherited the power to control the fires inside the mountain.
Amid all this variety, a number of themes keep resurfacing. One is man's destructive relationship with nature, which Dickinson was writing about long before environmental themes became vogue-ish. This is the underlying concern of The Changes trilogy, giving the final victory of science an ambiguous source. Dickinson has suggested that The Blue Hawk could be taken as a parable of the dangers of nuclear power; and it is tempting to read The Tears of the Salamander the same way. The Kin is a brilliantly imagined saga of early humans in Africa, struggling to understand what is "people stuff". Although commissioned for younger children - Dickinson's brief was "short sentences and lots of action" - it emerged as his most ambitious and intellectually satisfying book (though I was frustrated by shamanistic episodes, which seem to presuppose some form of ESP). Eva combines the two themes, the environmental and humanistic. Interestingly, Dickinson has said it generates 80 per cent of the letters he gets. A third theme is empire. The Dancing Bear, set in a vividly realised sixth-century Byzantium, The Blue Hawk and The Ropemaker all revolve around cruel, rigid, crumbling empires.
He is not at ease with high fantasy such as The Ropemaker; conversely, he no longer finds detective stories satisfactory: "Too much clockwork. It is writing in a verse-form which is so restrictive that you can no longer choose the words that mean exactly what you say." In any case, he no longer feels he has it in him to write an adult novel, though he has a children's novel and some short stories on the stocks. Listening to the pleasure with which he talks about it, it is hard to imagine him not writing. As he says, you live in your books.
Peter Dickinson was born in 1927 in Africa, where his father was a colonial civil servant. When he was about seven, the family moved back to England; shortly afterwards his father died, leaving his mother to bring up four boys. After Eton and Cambridge, he joined Punch in 1951. In 1968 he won the Crime Writers' Association Gold Dagger for his first novel, Skin Deep (US title: The Glass-Sided Ants' Nest), set among New Guinea tribespeople and anthropologists in London; he won it again in 1969 with a sequel, A Pride of Heroes. His first children's book was The Weathermonger (1969); among many others are The Blue Hawk (1975 Guardian award winner), Eva (1988), AK (1990 Whitbread Children's Award) and The Ropemaker (2001). He has been shortlisted for the Carnegie a record nine times and has won twice, for Tulku (1979) and City of Gold (1980). His new novel is The Tears of the Salamander (Macmillan). He lives in Hampshire with his second wife, American children's author Robin McKinley, and their whippets.