Terry Pratchett was somewhere else in Discworld when the line came into his head: "The Amazing Maurice and his educated rodents." The Carnegie Medal winner says: "I thought Maurice was a conman, and what kind of a con would you do with rats?" As he talks, the wonderful tapestry of invention that is his mind unfolds. Allusions, jokes and a kind of serious compassion (I wanted to call it "morality" but Pratchett hates the possible connection with Sunday-school respectability) jump through the conversation like a game of snakes and ladders. Up, down, twist, laugh. The way his books read is, it seems, the way they are written.
The result is the first Discworld novel for children. In the story, Maurice and his allies, the rats, don't just talk, but read as well. With Keith, a boy who plays wind instruments and seems none too bright, they work a scam lifted from the tale of The Pied Piper of Hamelin, the rats over-running town after town until Keith charms them away for a fee. It works until they reach Bad Blintz, where the mayor's daughter, Malicia, is a compulsive fantasist, and a much nastier rat scam is operating.
"Malicia is the kind of kid who goes through life, like 50 per cent of kids, maybe, with no friends, thinking she can find her way through with books," Pratchett says. He laughs: the recurrent theme in his 27 Discworld novels (including Maurice) is the entanglement between real life and fantasy, with all its delights and pitfalls.
Pratchett has great fun with the idea of rats who learn to read overnight but have no means of being selective about what they read (their Bible is a particularly saccharine picture book, The Adventures of Mr Bunnsy) and share a Martin-Luther-King-style dream of future rat-and-human co-operation. He adds to the mix Maurice, in whom language has bred an un-catlike conscience, and the evil Ratking. Along the way he makes some profound points about war, justice and intelligence.
"I saw photographs of a ratking (a phenomenon in which a group of rats'
tails become tied together) from a museum in Switzerland. The story began to move. All I had to do was put my hand on the steering wheel. Once you have your pieces on the board, important things happen, like emergent phenomena in physics, and you take advantage of them."
He has just been enjoying some more emergent phenomena. "My current heroine is called Tiffany," he starts to explain. "That name has associations that have nothing to do with the nature of the girl, more to do with EastEnders. But the name is related to "epiphany", meaning a revelation. She is a studious girl, daughter of a shepherd, living in a farmhouse on the chalk hills with only four books in the house, one of which is a dictionary. She reads the dictionary all the way through but doesn't know how to say any of the words. Her grandmother, a wise old woman, says the hills are 'in her bones', which they are in a way - the hills being chalk, and bones being made of calcium. But chalk is made up of old sea creatures, all crushed together, and Tiffany starts to become aware of this, all the sea voices calling to her in dreams. "So I found out that in Gaelic the words tif fanna can mean 'land under the sea' or, slightly differently, 'away with the fairies' - both of which fit her quite well." He beams. "It's those little Easter eggs you get sometimes when you are working; usually when you're doing the right thing."
Pratchett has done the right thing over and over again, selling 21 million books worldwide to readers of all ages. He was recently named as the UK's bestselling author of the 1990s. Children, particularly boys, are among his most passionate fans, perhaps because he never writes down to them. His nose for satire is keen, even when the satire is affectionate. The Wind in the Willows is the first book he remembers reading for pleasure, yet he was always struck by its inconsistencies: its clothed animals; a Toad big enough to drive a car yet small enough to fit down a mole hole. In The Amazing Maurice, he exploits the contrast between the innocent world of Mr Bunnsy, in which even a snake wears a collar and tie, and that of the talking rats, who soon discover that clothes are not suited to their lifestyle. Reading Richmal Crompton's William books as a boy, he discovered irony, the play between opposing world views and the sheer narrative gusto present in his own pages. He owns three sets of Tove Jansson's Moomin stories: like his own books, they can be read on many levels and are infused with wisdom under cover of playfulness.
All these, along with G K Chesterton's The Napoleon of Notting Hill, Brewer's Dictionary of Phrase and Fable, Jules Verne and Robinson Crusoe, have gone "into the attic (of his mind)", pulling on the levers on the way, waiting for a story to come and rummage. In the same attic, there's an "idyllic childhood memory" of learning to balance reality and fantasy. "If I close my eyes," he says, "I can still hear the sound made by the clouds in the aeroplane that flew you to Father Christmas's grotto in Gamages department store when I was five years old. The gnomes took you to this box, which had a roll of canvas with scenery on, unrolling past the window. I remember thinking, 'that is a roll of canvas, but it doesn't matter because we're going to see Father Christmas'."
Fantasy, the adult Pratchett believes, is the stuff of life. "If you grind up all the universe you won't find one molecule labelled 'justice', yet (justice) is such a powerful idea. Everything is permeated with fantasy."
His quintessential heroes may not be very likeable, or even seem very moral. But like Granny Weatherwax in the Discworld books, if they see something wrong they wade in to set it right. So, in a telling scene (Pratchett's own favourite) in The Amazing Maurice, the rat leader, Darktan, and the Mayor are talking about the burdens of leadership and how to realise their dream of a better future. Darktan sums up their agreement:
"If you're prepared to believe I can talk I'm prepared to believe you can think." The message is that if you're trying to do good, you can't afford to get hung up on a fancy notion of what doing good might look like.
Of course, we do all get hung up on such notions. For Terry Pratchett, that is where the fun begins. "As a jobbing author," he says modestly, "all I know is: here's an idea, where's the story? Here's a heroine, where's the man? Where's the humour? And then it takes shape."