Whether it is the mesmeric effect of watching a balloon on stage or whether they empathise in some profound way with the protagonist, I don't know. I certainly don't believe that you have to cast the children in a particular role as heroes or villains. A play for children should probably start through the eyes of a child and be child-centred, and should express very clearly what the child is feeling."Bright colours and loud music aren't what matters. I don't want to manipulate children in that way, whipping them up and exhausting them and then whipping them up again and again."Indeed, Clark has gone so far as to deconstruct the illusion of the red balloon's independence and autonomy and in doing so he has created something even more magical. I have seen tiny children sit through this play for an hour and a half with no bottom shuffling. Four years later his call was returned and he was given the all-clear. In the meantime, however, he had had to find an alternative show.

He chose Raymond Briggs's The Snowman, again because it was wordless and again because in it the child is cast in the role of an adult to show other children his intensely felt world. "All the mundane business of their world becomes special in the process of showing it to someone else," says Clark.He claims to know very little about children's theatre and even less about children. "What I do know from observing my own [four, aged from two to 11] is that you can't define the quality of their experience or underestimate what it is they find important or why. For children the world is much richer because they are working it out. Unlike adults, they don't jump to conclusions, bypass things or take a short cut." And he feels strongly that children's theatre should not attempt to do what in- yer-face television and Walt Disney can do better "It should be quite other. Where an adult may immediately want to cast the child as the protagonist in a rather sentimental way, a child will sometimes see him as selfish or a victim and their responses may fluctuate throughout."Unfortunately, Clark's initial efforts to track down the rights to The Red Balloon failed so he sent a letter to the only Pascal Lamorisse listed in the Paris telephone directory.

I hope that for a child what is seemingly a simple story is actually more complex. "Adults have always wanted to define the story as being about the spirit of the imagination, the loss of innocence or whatever But as a director I think to define is to diminish. "You can also make very ordinary things very important, so the finding of the balloon on the lamp-post - probably five seconds in the film - can be explored imaginatively so that the child wonders who it might belong to. Making the stage musical has for me been about exploring the potential of every moment, giving it as much resonance as you can."Unlike many pieces of children's theatre which strain - often too hard - to appeal simultaneously to adults and children, Clark has concentrated on the childish response, leaving adults to take what they want. "Putting it on stage has meant you can try to explore in more depth the frustrations, aspirations, contradictions and ambiguities of a child's experience," says Clark. People have said that it does that and more," says Clark.The film is wonderfully rich with suggestion and remarkably short of stated fact, which has allowed Clark freedom to flesh out the tiniest vignettes: the cat in the street that features for a second or two, the loneliness of the only child, the pressures of living in a flat where no pets are allowed, the observation that all the characters other than the children are very old. ("Balloon, balloon!" is, I recall, the sum total.) "It meant you could have a much freer hand while reflecting the spirit of the original.