This ‘drawn-out’ and ‘self-important’ film proves the musical didn’t need to be split into two parts

There are decent performances from Cynthia Erivo and Ariana Grande – but this flat opening instalment of The Wizard of Oz prequel may not convert those who aren’t already super-fans.

One of the key things to know about Wicked, the big-screen adaptation of the smash-hit Broadway musical, is that it’s not actually a big-screen adaptation of the smash-hit Broadway musical: it’s an adaptation of the first half. The title, on the screen if not on the posters, is Wicked Part One, and it ends with the caption “To Be Continued”, so viewers should be warned. We’ve had similar tricks played on us by the makers of Mission: Impossible – Dead Reckoningand Harry Potter and the Deathly Hallows, but it’s still frustrating to realise that you’re only halfway through the plot after two-and-a-half hours, and that Part Two won’t be in cinemas for another year. It’s like being turfed out of a theatre at the interval.

Whatever the film-makers’ reasons, you can’t help resenting their arrogance. The implication is that their narrative is so profound that it demands a full five hours of screentime. And Wicked won’t convince everyone that that’s the case.

For the benefit of those who haven’t seen the show, which premiered on Broadway in 2003 and has been running ever since, it’s a spin-off of L Frank Baum’s The Wonderful Wizard of Oz, which delves into the back story of Glinda the Good and the Wicked Witch of the West. It begins near the end of the classic 1939 film, The Wizard of Ozwith the Wicked Witch having been dissolved by water splashed on her by Dorothy. Glinda visits the Munchkin village to share the glad tidings, whereupon the Munchkins ask her about the friendship she had with the Wicked Witch in days gone by, back when her name was Galinda. And so begins a tale that is best described as Harry Potter meets Mean Girls. Mostly set within the Italianate walls of Oz’s off-puttingly named Shiz University, it charts the relationship of the put-upon Elphaba, played by Cynthia Erivo, and the confident Galinda, played by Ariana Grande-Butera (ie the pop star known as Ariana Grande, but credited onscreen with her full name).

Elphaba was born with pea-green skin, so she has always felt like an outsider. Her telekinetic powers, which spring into life whenever she is angry, don’t help matters, either. And, in fact, she has only come to Shiz University to keep an eye on her sister (Marissa Bode), who uses a wheelchair. Galinda, meanwhile, is the archetypal American queen bee, a clothing-obsessed blonde who is adored by everyone around her almost as much as she adores herself. These two loathe each other as soon as they are forced to share a room – they even sing a duet on the subject – and the situation is exacerbated when the university’s sorcery teacher Madame Morrible (Michelle Yeoh, who is no singer) favours Elphaba, and the handsome Prince Fiyero (a scene-stealing, swaggering Jonathan Bailey) favours Galinda. Or does he?

If you’re already a fan of the musical, you’ll probably be happy with the painstaking job that director John M Chu (Crazy Rich Asians, In the Heights) has done in transferring it to the silver screen. There’s a slick screenplay by Winnie Holzman and Dana Fox, the songs by Stephen Schwartz are big and rousing, and you can tell that armies of craftspeople have laboured for days over every wig, embroidered jacket, and decoration on the colourful, gleamingly artificial set. The two leads are well cast, too. Erivo is disarmingly sweet and vulnerable, while retaining a hint of latent menace, and Grande-Butera, who can hit notes so high that only dogs can hear them, is amusing as a blithely perky narcissist. She would have been an interesting Barbie if Margot Robbie hadn’t played the role.

If you’re not already a devotee of the musical, though, you may not be converted. The film ends with a song called Defying Gravity, so it’s only fair to say that that’s precisely what Wicked doesn’t manage to achieve. It doesn’t take flight. It doesn’t have the terrific jokes, the startling twists or the stunning dance routines that might have cast a spell on you, and it’s weighed down by under-developed subplots and under-used supporting characters (who presumably have their moment in Part Two), as well as by its own sense of self-importance. With every lung-busting empowerment anthem, Wicked seems to be declaring that it’s a significant work of art. And yet the message about not mistreating people just because they have green skin isn’t exactly subtle, and the questions the film answers aren’t exactly urgent. Why does Elphaba wear a pointy hat? Why did Galinda change her name to Glinda? How can the flying monkeys fly? Why is the yellow brick road yellow? These aren’t the most vital issues in the world, but if you are keen to see a Wizard of Oz prequel, I’d recommend Sam Raimi’s Oz the Great and Powerful, which came out in 2013.

Wicked is drawn-out and bland in comparison. It might have been lighter on its feet if the editors had cut a subplot about magical talking animals, which doesn’t add anything except several minutes of running time. And they could have cut Elphaba’s sister, who is given perplexingly little to do. That way, the film could have been packed the whole musical into one fast-moving, satisfying entertainment. As it is, I have a strong suspicion that Wicked will work much better as the first part of a double bill, with Wicked Part 2 being shown after an interval. But we’ll have to wait another year to know for sure.

Wicked is released on 22 November in UK and US cinemas