It would be good to think that some of the Glasgow primary schools that flocked to the Theatre Royal to see Roald Dahl’s The Witches were there because their pastors remembered seeing the same company at the same theatre five years ago doing The BFG. The company is The Clarion, but the name to remember is its writer and director, David Wood.

He is the nearest thing we have to a national dramatist for children - 25 years in the business, the author of 30 plays, and still blazing with a zeal for the form. He writes in the programme that “children are our most important audience and deserve the best we can give them’’ and then delivers a gobsmackingly good production.

The Clarion achieves the production values of the best adult theatre. That should not be such an extraordinary notion but, as David Wood suggests, too often children’s theatre companies “insult the audience by cutting corners, economising on production values and making the excuse that it doesn’t really matter because it’s only for kids”.

So, if children smell like fresh dogs’ droppings to the witches, then this production fairly reeks of scrupulous professionalism, from doors you can slam without wobbling the coving to frogs that hop like frogs, and a practised accuracy of ensemble playing that never wavers.

In a talented cast, two performances stand out: Karen Briffet as The Boy defies age and sex so cleverly you read the programme twice to be sure; and the Grand High Witch, played by the knife-like Katerina Jugati, had gleamed so viciously that even her sweet smile at curtain call failed to reassure some in the dress circle.

But good storytellers such as Dahl save the best for last, and so do I. The witches can do magic. They turn the boys into mice, right there, before our very eyes. The spell is put on them, and they shrink. Whip the cloth away, and there they sit, no bigger than a man’s hand, their little noses quivering.

It has been an engrossing first act, the toffees are uneaten, the audience is fascinated. “How is it done?’’ asks a Primary 4 pupil behind me. “I don’t know,’’ his friend sighs in despair. And to be honest, neither do I, but it helps to know that the illusionist is Paul Kieve, a gold star member of the Inner Magic Circle.

Brian Hayward