The Witches review – frights played for fun in rollicking musical

In Roald Dahl’s universe, witches are the most dangerous of all the living creatures on Earth. Disguised as ordinary women (think Beelzebub as a lollipop lady or air hostess), they are as “bald as a boiled egg” with square feet and a predilection for “squelching” humans – particularly children.

In the world of this musical adaptation, they look as if they have stepped out of Stepford in their pastel twin-sets and gloves: a middle-aged, British equivalent of Mean Girls.

The story revolves faithfully around young Luke (Bertie Caplan on opening night), who ends up living with his libertine gran (Sally Ann Triplett). She has not so much an interest as an obsession with witches and all her learning comes into force when they find themselves accidentally at the heart of a coven, in a Bournemouth hotel where the witches are plotting to turn Britain’s children into mice.

There is fun, wit and imagination in Lyndsey Turner’s production. If this story is Dahl’s barely disguised diatribe against enforced female conformity, all the better. We have a delightful antidote to the Stepford women in cigar-smoking gran, wonderfully embodied by Triplett with an edge of vulnerability that does not appear in the book.

Lucy Kirkwood brings the magic through a script stuffed with effervescent one-liners. Dave Malloy’s songs (with lyrics by Malloy and Kirkwood) sound as if they are still in development, sometimes oddly tuneless and accompanied by thin piano notes or a stomping orchestra. In some cases characters half-sing and half-chant with hammering repetition.

A couple of storming numbers are tucked in between: Bruno Sweet Bruno, a fantasy about a sugar high, gets the feet tapping and is sung sensationally by its chocolate-loving namesake (Cian Eagle-Service). Eagle-Service plays Bruno as a posh underage ladies’ man (oddly, he pulls it off) and is one of several child performers with an astounding voice tonight, including Jersey Blu Georgia, who plays the gnome Helga come to life.

There is a sultry number in Wouldn’t It Be Nice? sung by Grand High Witch (Katherine Kingsley). An anti-child manifesto, its lyrics glint with comic menace. It is a shame this musical alchemy does happen more often.

If the script channels Dahl’s linguistic agility and imagination, it cleans up his darkness. The witches are more comical than abominable and there is a lo-fi cutesiness to the children’s transformations into inanimate objects (they pop sweetly out of boxes in cardboard costumes). The biggest fright comes when a phone rings in the auditorium and the High Witch loses it.

The performances are strong nonetheless. Caplan is lively as Luke, though the tender grandson/grandmotherly bond seems slightly lost, while Kingsley is a pleasure to watch – a dominatrix in a pastel suit, it seems at times. The hotel manager, Mr Stringer (Daniel Rigby), is seemingly trapped in his own sitcom (it could be Fawlty Towers or Hi-de-Hi!).

Lizzie Clachan’s revolving set brings around the scenes smoothly but the pace still sags in the second act. It is Kirkwood’s rollicking humour that carries us. You may not be scared but you’ll certainly laugh.

• At the Olivier theatre, National Theatre, London until 27 January