The creator of Mary Poppins, PL Travers, once gave a Paris Review interview in which she considered the popularity of her work: “I suppose if there is something in my books that appeals to children, it is the result of my not having to go back to my childhood; I can, as it were, turn aside and consult it. If we’re completely honest, not sentimental or nostalgic, we have no idea where childhood ends and maturity begins. It is one unending thread, not a life chopped up into sections out of touch with one another.”

Echoing her thoughts, James Joyce once wrote, “My childhood bends beside me.”

The best writers for children know this, instinctively, and Charles Causley is among the very best. The last poem in his marvellous, carefully arranged Collected Poems, begins “Who is that child. . .?” and with characteristic, illuminating mystery ends, not with an answer, but with a further question: “When I draw near him so that I may hear him, Why does he say that my name is my own?”. The adult, reading this, will recognise it as a way of saying that the child is father of the man, while the younger reader responds to its riddling intimations. The poemis for both of them, as indeed the whole book has been.

Causley is, of course, a traditional poet as we are reminded by a glance at the various sections - “Come out to play”, “Charm and Flower”, “Time and Places”, “Season and Festival” and so on - but he is also an unmistakably original one. His great gift has been to modify the tradition with a distinctive wit, often sly and mischievously ironic, and with a rhythmic verve and inventiveness which makes fresh news out of the old story.

He is a master of the haunting refrain, and many of his most memorable poems - among them “By St Thomas Water”, “Tom Bone”, “What has Happened to Lulu?”, and “Nursery Rhyme of Innocence and Experience” - explore themes of mortality, betrayal and loss from the viewpoint of childhood experience with never a hint of adult knowingness. It is more a case of knowledge informing the poems, which children will come to share in time, and Causley’s echoing allusiveness - to Housman, indirectly, in “If You Should Go to Castor Town” or Wordsworth’s Lucy and Belloc’s Ha’nacker Mill (I guess, directly) in “Photograph” (“She walks among time-beaten stones”) and “Under the Hawthorn” (“As she sits under A failing sun. Never a body. Never a one”) - is simply a measure of his skill at winding poetry of the past into that unending thread. Auden once described his craft as “breaking bread with the dead” and my guess is that Causley, for whom the past is never another country, though it is often most poignantly the Cornwall of his youth, would agree.

Perhaps, though, one shouldn’t overstress the numinous. Causley is also a superbly observant comic poet, and almost as many poems end with a sardonic twist as with a lyrical frisson. He is the least solemn of moralists and relishes absurdity. Like Parson Hawker of Morwenstow who dressed in a mermaid’s skin, to the credulous amazement of all who saw him,and afterwards “smiled and pondered As he went upstairs to bed on the gullibility of man, And sadly shook his head”, Causley understands human folly but is as likely to nod with wry amusement as to shake his head. He loves nonsense (there are many echoes of Lear in his work) and there is nothing he likes more than a rumpus in the peaceable kingdom.

Both these books are a joy, but it is impossible, when reviewing them together, not to say go for the Collected. Dancing in to the tune of almost 400 pages, it is a beautifully-produced treasury of essential reading. John Lawrence’s illustrations, arranged in his familiar manner of including all the vignettes from a particular section in a full-page tapestry preceding it, work wonderfully. Like the poems, they are full of character - and characters - populous but never overcrowded. They offer an object lesson for illustrators in how to work with a poet.

As for Going to the Fair, perhaps the most interesting thing about it - which returns to the point I made at the beginning - is that it is has been chosen by Causley himself, as the dust-wrapper points out, “not only from his work for children but also from appropriate adult collections”.

The same goes for the Collected, of course, which one imagines could have been larger still. It would be fascinating to know what poems nearly made it, and some of the reasons for excluding them.