I didn't know Andrew Lloyd Webber still had it in him. The composer who started out with Joseph and the Amazing Technicolor Dreamcoat and followed that up with the rockier Jesus Christ Superstar has more recently been associated with an operatic grandiosity that is to the light-footed, great American musical what Brian Blessed is to a game of Chinese Whispers.
The anthemic cod-arias that have characterised many a Lloyd Webber production over the past decade or three here give way to the power guitar riffs of failed rock-band musician Dewey Finn, the hero of the 2003 Jack Black movie on which this musical is based.
At this show's core is David Fynn, who replicates Black's immensely likeable version of slacker Dewey down to a tee. It's a performance in which the rotund, endlessly energetic Fynn bounces around the stage like a space hopper without a driver. His Dewey may be cuddly but every sweating pore of his body - and there are a lot of them - yearns to be an AC/DC-like rock god. The fact that he wears knitted tank tops somehow only increases his credibility.
Unable to pay the rent, Dewey inveigles his way into a posh American school as a supply teacher. His charges are terrifyingly studious. But when he discovers that most of them can play an instrument he sees his chance to form a rock group and compete in the (apparently really famous to rockers) Battle of the Bands competition.
Laurence Connor's production - a hit in New York - takes off in earnest from the moment the child characters (each played by a rotating three-strong cast) take hold of the show. They are the progeny of tiger parents who don't pay $50,000 a term for their children to have fun. Any fun. But at its heart the plot has a feel-good moral, which is that everyone can be changed for the better when they encounter those with opposing attitudes to life - or something.
Dewey's slacker instincts are infused with a work ethic by the conscientious children; while the children, whose personalities have been suppressed by the ambition of their parents and school, suddenly find self-expression through Dewey. Everyone's a winner. But it's the kind of story - adapted by Julian Fellowes from the movie - that requires a good deal of incredulity to be suspended. Or rather, the way the story is told does.
It is Dewey's utter irresponsibility that is the narrative and comedy focus here. "You're late," the icy school head Mrs Mullins (Florence Andrews) informs him, to which Dewey responds with a shrug of teenage indifference. It's funny. But what would be funnier, I venture, would be a Dewey who knew that his livelihood depended on doing the one thing that comes least naturally to him - being responsible. Instead, he blunders his way through school in much the same way he blunders everywhere else. I know; it's only a musical and a comedy and I should lighten up. Just "go with it", seems to be the rather Dewey-like attitude embedded in this show.
If you can, there is much to enjoy. The kids are the real thing. A recording of Lloyd Webber's voice assures us that all the children play their own instruments. To prove it, the band down tools and stand like fans on a balcony overlooking the stage. As for Lloyd Webber's score, it's good - as are Glenn Slater's lyrics - if melodically rather predictable. And it's certainly not as good as Tim Minchin's score for that other school-set musical, Matilda.
Here, the intended show-stopper is clearly Stick It to the Man, which has the spirit of Alice Cooper's School's Out Forever, only with a much less infectious tune. For my money You're in the Band, sung by Dewey as he auditions his class of timid swots for heavy metal, is funnier and catchier. Nitpicking aside, the show's a winner.