That's right, you guessed it, the new Take That musical is a cheerfully bogus but sometimes spectacular exercise in asset-stripping. How could it not be, following Mamma Mia! and We Will Rock You, the most hardy examples of turning a band's back catalogue into yummy theatrical sundaes?

The only question for the ardent fan turned cautious theatregoer is just what calibre of cheerfully bogus spectacle are we dealing with here? “Great fun,” cooed contented consumers around me, after two and a half hours of plaintive power ballads, Hi-NRG romping and ho-hum humour. And if thoughts of Gary, Robbie, Mark and the other two's Nineties chart supremacy make you turn all gooey inside, what the hell, go with the flow.

Never Forget broke box-office records on its regional tour last year. But, while it's played at a zip and sung with a smile, it's terrible old cobblers and it knows it. What's more, it knows we know it, and strongly suspects that we don't mind.

The writers - Danny Brocklehurst, Guy Jones and Ed Curtis - have weaved 16 songs around the story of a Mancunian Take That tribute band, whose members all need to succeed.

There's Ash, the peroxided romantic lead, played with a suitably Gary Barlow-like blankness by Dean Chisnall. He's the main singer, targeted for a lucrative solo career by a voluptuous vixen from a talent company. Cue ructions with his fiancée, Chloe, and his new bandmates - a cheeky Robbie, a square Mark, a thick but buff Howard and a comically lisping Thpaniard as Jason.

The songs slip in without the clunk of some catalogue shows, but, really, why even bother? There's no dramatic darkness to give the tunes more heft when they arrive; the attempts at comedy are affable but blunt. “Think I'd make a good Gary Barlow, do you?” says Ash. “More like Ken Barlow,” he's told.

When the songs are delivered, full on, they're pretty good. None of the singers exactly makes the cavernous Savoy his own. But ripping through A Million Love Songs, Relight My Fire, It Only Takes a Minute and Babe - a stand-out in Gary Barlow's efficient rather than exhilarating oeuvre - they hold the stage.

The staging is lively, the choreography does the job, and there's a rainy Back for Good sequence that replicates the song's video - cue the biggest whoops of the night. And then Ed Curtis, the director, gives us a genuinely spectacular stunt with falling rain, and for a moment we are all taken out of ourselves.

The best and most honest moment is the megamix encore. With all of the 30-strong cast facing forwards, selling these electrodisco tunes with everything they've got, this ersatz spectacular comes alive. The spoken moments are no more convincing than the plot points in a porn film. But when this tribute band actually does its job, buoyed by £3million of theatrical resources, you get a sense of the simpler, stronger show that Never Forget could have been.

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