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The 3D concert movie may be a relatively new phenomenon but it already has a template: backstage shenanigans, endless travel, bellowed numbers shot on multiple cameras before legions of baying fans.

One-on-one access to the act/group in question is a given. But it’s normally confined to snappy sound-bites and blatantly staged situations designed to show them in the best possible light.

The makers of Katy Perry: Part Of Me were not to know its subject would have a messy marital break-up in the middle of filming what was no doubt conceived as an upbeat, big-screen cash-in on her phenomenal recording success.

Wisely, though, they’ve turned it to their advantage, using the star’s emotional distress to add some heart and honesty to what would otherwise have been a sterile exercise in brand promotion.

The irony is it’s another sort of Brand – the Russell variety – who ends up being the pic’s most intriguing (non-)presence. Largely invisible apart from a couple of grudging cameos (think Warren Beatty in Madonna’s Truth Or Dare ), he’s the elephant in whatever room his ex-in-waiting happens to occupy over the course of her year-long, 124-date California Dreams tour.

he upshot is the concert scenes appear peripheral, not to mention naff with their candy-bright outfits and foam-firing cannons. Which is a pity, as the material itself – yelping signature track ‘I Kissed A Girl’, ballsy ballad ‘The One That Got Away’, floor-filling anthem ‘Firework’ – is actually pretty strong.

Katy nuts will lap up every oddball remark, tearful jag and elaborate routine. For the rest of us, Part Of Me proves unexpectedly instructional in its glimpses of how pop stars are constructed.

The bubbly, bewigged Perry we see today only came about after attempts to package her as a gospel goody-goody, grungy Alanis clone and Avril Lavigne-style rock chick were greeted with indifference. So might this, in fairness, but that doesn’t prevent it from being a cut above the usual music bio-doc.

Neil Smith is a freelance film critic and writer who contributes regularly to Heat, SFX and Screen International. He's a long-time member of the London Film Critics’ Circle and was a contributing editor at Total Film for many years.