For children, Quentin Blake remains the greatest draw Does any literary term trigger so much pleasure as "picture book"? I often feel my visits to great galleries have had less effect on my visual imagination than the instant permeation, aged four, of Arthur Rackham's wild-eyed, grasping trees in my battered volume of English Fairy Tales. The truth is, most of us will spend more hours enraptured by Beatrix Potter, Ernest Shepard and Maurice Sendak than we will ever spend in the esteemed company of Botticelli and Constable. In any case, who can be sure where art ends and illustration begins? Paula Rego's outlandish figures would grace any fairy tale, while Little Tim's Edward Ardizzone was a noted war artist. The distinction between art and illustration seems particularly irrelevant in the case of Sir Quentin Blake. Which other living person has had such a seismic impact on the collective visual imagination of Great Britain? His collaboration with Roald Dahl brought him worldwide acclaim, and many Cambridge-dwellers remember the university's 800th anniversary more keenly for Blake's celebratory artworks than for any scholastic achievements. Even better, though, is the rare treat of viewing Blake's work in all its inky, spellbinding actuality. Cambridge's Fitzwilliam Museum has just opened an exhibition of Downing College's favourite son: Quentin Blake: Drawn by Hand. The show coincides with half term, runs until May, and parents will be glad to learn it's a joy for children; not a Dahl-fest, but a measured look at Blake's energetic output over the past decade. My eight-year-old was mesmerised by an illustration for David Walliams's The Boy in the Dress, while I adored the mother and baby capering underwater in an umbilical paradise, commissioned for a maternity ward. There's such vivacity in Blake's fluid yet ink-splattered line and his blotchy application of colour. "How can he be so simple, but so complicated?" asked my niece in wonder, vowing to get her nib pen out as soon as she got home. The answer lies in Sir Quentin himself, still quietly impish at 81. I managed to commandeer a brief audience with him at the show's opening. We talked about the late Ronald Searle, with whom Blake shares an anarchic inventiveness and a love of France. I couldn't help asking if he shared Searle's fondness for champagne, too (the cartoonist promised his future self a daily glass while a Japanese prisoner of war). Not only was champagne indeed a shared taste, Blake told me that when he won the Eleanor Farjeon Award he spent the prize money on Searle's favoured brand: Billecart-Salmon Brut rosé. As with all the most interesting children's writers and illustrators I've met, Blake isn't a cosy person, so much as a puckish and watchful one. He admits his art doesn't arise from a special fondness for children: "You've got to be able to identify with them, which is a different thing." What Blake enjoys about children's books is that "they lend themselves to metaphor and are very often fables." Anyone who has read Blake's own Zagazoo, where a sweet baby starts shape-shifting as it grows up, until it becomes a hairy teenage monster, will grasp what he means. Blake became most animated, however, when we touched on the recently abandoned EBacc and a perceived attempt to downgrade art and music. His eyes blazed as he fumed at the politicos who talk about "literacy" rather than literature and don't recognise the value of installing a passion for art in our children. "They think it's about self-expression," he said with disgust. They don't see it's an imaginative, emotional and moral discipline. Anyone who witnesses the children's rapt faces at the Fitzwilliam will have no doubt about the truth of Blake's words.