Picture books offer a valuable first experience of art appreciation and although they come in truckloads, there is seldom any opportunity for critical discussion, and the skill behind the artwork tends to get taken for granted. Review space is limited, and cheerful flurries of unqualified praise - “exuberant”, “brilliant” and so on - do little to stimulate curiosity about the pictures. But, with perceptive observations on his 50 years at the drawing board, that’s just what Blake does in Words and Pictures.

It’s a big book with the spacious airy design that’s common to all his work; bursting with illustrations, but “with lots of elbow room” as Blake himself might say.

Apart from life-drawing classes in his 20s, Blake had no formal art training, but even as a schoolboy he was successfully submitting drawings to Punch: early work includes some remarkable A-level drawings and a wonderful parade of book jackets and cover designs for Punch and the Spectator that show the inventive wit and the graphic economy that even then defined his style.

For many years he was head of illustration at the Royal College of Art and he’s an easy, unpretentious, entertaining communicator who knows how to make himself understood, in both words and pictures (this is one reason why he’s been a success as the first Children’s Laureate). He talks illuminatingly and uncomplicatedly about the development of his own career.

Working in so many areas of illustration, for adults and children, he likens his progress to that of a medieval apprentice, learning as he went along, receptive to all kinds of influences - Daumier, Picasso, Goya, Rowlandson, Cruikshank, Andre Francois, Ronald Searle. Using a theatrical analogy, he says that a double spread is like “an empty stage” for his characters, and in his wordless book Clown, the characters communicate with mimed gesture inspired by the Marcel Carne film, Les Enfants du Paradis. And there are many literary influences too: Ionesco, Beckett and Joseph Conrad, whose book The Shadow Line helped him create his 1998 picture book, The Green Ship.

On a practical level, he describes how he first learnt the importance of capturing, in a finished drawing, the “atmosphere and expression” of the roughs, how he subsequently perfected this technique with the use of a light-box, and ow, with an insatiable appetite for drawing, it’s possible to become relaxed enough “to live through the pen you are holding in your hand”.

As you can see here, on every page, his drawing is like handwriting, the character of the line effortlessly adapting itself to the demands of a scratchy nib, a fibre tip pen, a plastic toothpick or a blackboard chalk: here you can find urgent squiggly emblematic roughs in felt tip, tender life drawings done with a brush, and a magnificent bird of prey vigorously drawn with a quill cut from a vulture’s flight feather.

He explains how he starts a book with rough layouts and describes how preliminary drawings will sit on his desk “silently criticising one another”, he muses on the “balance of power between line and colour” and demonstrates the “atmospheric” properties of watercolour washes.

And he emphasises the importance of a robust text: “being jumped up and down on is what, metaphorically at least, happens to the words of children’s picture books: they are made for constant repetition”. Blake has worked with many writers, and although, as he says, the collaboration is with the text, rather than the author, there are entertaining (illustrated) snippets of his correspondence with Roald Dahl as certain characters - such as the alarming Miss Trunchbull - took shape on the page. And he describes how his indecision concerning the BFG’s footwear was resolved when a parcel arrived containing one of Dahl’s own vast Norwegian sandals.

Along with all the familiar characters, and a wealth of hitherto unpublished illustrations, Blake gives a generous account of every aspect of his work - to go behind the scenes like this is to learn the extent of the planning that lies behind the apparent insouciance of that famous freewheeling spontaneity. Sadly for researchers and browsers, there’s no index - frustrating in a work so richly packed with names, dates, technical details and anecdotes and, of course, a staggering wealth of illustrations - but there is an extensive bibliography and a useful biographical resume.

Of unique value to students, primary school teachers, art teachers and aspiring and practising illustrators, this hugely readable and inspiring book is also a vital addition to the family bookshelf in any home where picture books are valued, and where the art of drawing is something to be celebrated.