Let’s get one thing out of the way; the first five minutes of this film will make you want to kill yourself. By any means necessary, even if it’s taking a whipped cream-filled bra to the head. The film opens with a typically narcissistic five minutes of watching Katy Perry’s finely-honed buttocks prance around a vast dressing room in a costume which most closely resembles the Christmas tree of the Jetsons, fondling her rotating nipples and all around loving life, as you would if somebody paid you to prance. For other people, that’s stripping – not so for Katy Perry. So far, so insufferable. On that front at least, Part of Me certainly delivers; no expense is spared in showing us extensive, impressive concert footage, the entirety of the MAC counter Katy carries around on her face for every performance, perfectly proportional to the rhinestones on her tits, and a fanatical love for her which is shared by everyone she pays to work for her.

Expected too is the tour down Jesus Christ Boulevard – Perry’s upbringing by travelling Pentecostal church ministers is covered in detail, as is her brief gospel career, and her ‘wild’ period in her early 20s. It’s here that you start to shift uncomfortably in your very expensive 3D seat; Perry’s wild 20s look a hell of a lot like everyone else’s – unfortunate booze, outfits and significant others all feature, complete with a devotion to Alanis Morissette circa You Oughta Know. Something in common? With this plastic pop-tart? Excuse us whilst we re-evaluate every single one of our life choices.

Unfortunately enough, the cotton-candy world in which her earnest young fans so happily live starts wrapping you up in its sugary sincerity faster than you can say ‘T.G.I.F.’. Her rather tricky and exploitative journey to becoming Daily Mail fodder is clear. There’s a moment where you watch a barely-legal Perry playing in a smoky bar, and her pitiful little mug, devoid of foot-long fake eyelashes, is singing an acoustic version of what hardcore fans will recognise as One of the Boys filler track, Thinking of You; she looks, for all the world, like poor naked Jenny singing Bob Dylan in Forrest Gump. Juxtaposing this broken girl with the woman who claps her hands with glee at the thought of a Japanese teashop which comes complete with cats, and you feel like you want everything in the world that is good for her. Add in the constant stream of gorgeous, wide-eyed children who have blissfully fallen head-over-heels into the universe of sweets and positivity and perpetual LSD trip that Perry has so carefully cultivated, and you simply want to believe her, because they do.

However, where this differs from its predecessors, such as Justin Bieber’s Never Say Never, is that under all that enjoyable artifice, Perry allows a view inside her personality which perfectly toes the line between honest and patronising. She doesn’t claim to ever have been bullied, to ever have known poverty or to have been anything but beautiful, and that’s exactly what makes her breakdown over the end of her marriage a genuine heartbreaker to watch. Weeping in a onesie, a familiar foetal position wedged into a pink penguin suit, Perry’s devotion to her fans is shown to be nothing short of colossal – she cries right up until the platform rises up for a Teenage Dream to which she can no longer lay claim.

As for the consistent interjections of radio-ready tuneage, it’s not even as if she is lipsynching over re-recordings of her hits that sound live; she’s a competent entertainer, whether you like the songs or not. Rapport with the crowd in crowd-pleasers such as California Gurls is yet another warm and fuzzy Hello Kitty legwarmer on the calf of this film, and other highlights include her jazz reworking of chart-topper I Kissed A Girl and a surprise guest during Last Friday Night (TGIF) who will make you want to hug a kitten till it dies.

In conclusion, the advertising is far, far more obnoxious than the actual film. You are completely right to sneer at the whole ‘be yourself’ schtick. Whether a feat of masterful cinematic manipulation or not, to judge Perry based on our own plebeian scale of reality and rational behaviour is silly; of course she’s not normal in any respect; she’s a popstar. You can’t be normal under a lens that zoomed. She’s retained a lot of what does make a person a person, and shows you that without including tacky footage of hers and Russell’s arguments or of her taking a dump.

In fact, the only person who actually hates Katy Perry at the end of the film is her own grandmother, who is the single most hilarious relative of a celebrity ever shown on screen. Mostly because she is a walking, talking “fuck you” to her granddaughter and everything she stands for, and has been waiting to die, in vain, for at least two decades. That alone makes this worth seeing, and also that it’s marginally better than the Justin Bieber one (which we also liked), and you’ve got to get your shameless pop-kicks somewhere until the Queen biopic comes out. WHICH SHE MIGHT EVEN BE IN.