The Museum of Modern Art at Oxford has often been the venue for unusual events, but the happenings of the past month must have been among the oddest it has seen – sixty children wielding brushes, attacking a vast mural under the exuberant direction of Jan Pienkowski, small groups producing meticulous, collectable drawings with Helen Oxenbury or piles of ephemeral splashes with John Burningham. These were all an accompaniment to ‘SMagic, the recent exhibition of illustrations from children’s books, which brought colour and chaos to the Museum’s back room.

The whole idea of such an exhibition, originally intended merely as a summer event, seemed to raise queries and raise hackles. Surely illustrations belong on the page, not on the wall? How can you gauge the success of an illustrator by one example when the effect is cumulative throughout a book? Isn’t this wrenching a child-oriented craft into a solemn ‘art’ discipline? These concerns and subsequent discussion gave the exhibition added edge.

Some illustrators immediately meet and keep the interest of adults and children – how do they do it? What is the key to those images, now instantly recognisable by thousands, like Mr Gumpy in his green punt outside his green house with its wide, watery veranda? Within the book and bound to the text, the Mr Gumpy illustrations succeed by virtue of their economy, repetition and variation, and understated comedy. Yet out of context the skilful composition, witty use of detail and inspired use of colour make the original an enduring and satisfying little painting, which shone like a window into a hidden garden in the middle of the exhibition. Mr Gumpy’s secret – or rather John Burningham’s – is that he combines familiarity with wonder. The same is true of another superlatively successful figure, Raymond Briggs. Represented at Oxford by a Fungus the Bogeyman Christmas card, showing ‘smelly THINGS’ being placed in the bed of a Dry-Cleaner, Briggs exploits the element of surprise, either by attacking all five senses as with Fungus; or by making the reader create his own story, as with The Snowman; or by creating a familiar world for a mythic figure, in the details of his Father Christmas stories. And surprise is also one of the strengths of Quentin Blake – irreverent, energetic, always with ‘us’ against them – a point of identification he shares with a more realistic but equally mobile and vivid illustrator, Shirley Hughes.

One often hears that some illustrators may be ‘too clever’ for children. I doubt it. It is true that Nick Garland’s black and white graphics, or Nicola Bayley’s exquisite watercolours do not capture a young child’s attention at once, but when they do, they retain it; and one feels that if Bayley were invited to illustrate classic children’s literature, her talent might influence the interpretation of a whole generation of children. On the other hand, some artists seem to wake up adults via the children, like Amanda Vesey whose Gloria the Goat appeals immediately to young readers so that their enthusiasm makes one look again at the skill and charm which lie in ‘artless’ simplicity.

But for non-readers and for young readers who like to pore over and re-read their books, the favourite artists are those which provide layer upon layer of new interest. Some simply present ‘odd things in corners’, like Joseph Wright’s dog ‘What-A-Mess’ with his band of tiny anarchic followers: the kangaroo on the bicycle in David Armitage’s Grandma Goes Shopping or the cow on the aeroplane in Colin Wildsmith’s Daisy. But you can be required to look for the strange in less obvious ways. An artist like Ardizzone, for instance, could ask readers to look into a picture which told the same story as the words, but in a different key – a slightly subversive one, wilder, stranger than the text. Or Helen Oxenbury, apparently portraying a hilarious, care-free ‘real world’ of playgroups, holidays, shopping trips, can suggest through detail the hidden inner lives of individuals and the assumptions and tensions of a whole society – the bandage on the fat piano-player’s leg; the upturned, anxious eyes of the black woman clutching her baby in the doctor’s crowded waiting room.

With other illustrators the invitation to discovery moves further into fantasy, yet still suggests comprehensible, if inarticulate emotions and ideas, as in Michael Foreman’s kitchen, invaded by trains, giant boots and boats, leaving adults cowering behind the door; or Satoshi Kitamura’s attic, with its dark spaces and huge spiders. This is a world where, as in Kitamura’s Angry Arthur, a child’s imagination can literally destroy the universe. A different set of pictures unlocks new elements in the fantastic itself, in fairy stories, songs, legends, so that these too appear anew. Among the most memorable pictures in the exhibition were Harold Jones’ simple and strange re-setting of ‘Silver Bells and Cockle Shells’ in a clear under-sea world; Tony Ross’s Goldilocks, hair-on-end, confronted by massive, looming white bears, claws and teeth bared; and Tamasin Cole’s idyll of a lime green dragon in affectionate dispute with a diminutive George. The famous fantasist of our day is, of course, Maurice Sendak, whose influence was evoked at the Museum by a group of prints, including some from Where The Wild Things Are. But equally remarkable is the British super-realist Peter Cross, whose glowing portrait of Podd the Trumpet wiring up the crocus bulbs was a highlight of the show.

Looking hard at illustrations makes one aware of the way children’s imaginations are asked to create fictions visually, stepping cautiously back and forward over the borders between the ‘real’ and the ‘unreal’. Seeing the pictures unfettered by the text is the way the smallest readers see them: for them the black and white hieroglyphics are often a mere border to the main, visual story. ‘SMagic, while it provided no answers to questions about artistic disciplines and status, or text and counter-text, may have helped many older readers to see the books afresh.