(Herald rating: * * * *)

Does Hogwarts do school reports? If so, the one for Harry Potter's third spell on the big screen might be: "His work shows a sound improvement. Pity he didn't apply himself earlier."

For both Daniel Radcliffe as Harry and HP3 itself take some giant steps up on the franchise's earlier instalments.

Here, the leading three of Radcliffe, Watson (as Hermione) and Grint (as Ron Weasley) all look and sound like the young teen whizzes they are meant to be depicting rather than auditionees for the Famous Five they have been in the past.

And as a whole, Azkaban breathes deeper.

It feels less bound to J.K. Rowling's pages but it illuminates her imaginings all the better. It's less the intermediate step between Potter the publishing phenomenon and Potter the theme park which the previous two sometimes resembled.

Yes, with edgy Mexican Cuaron getting into the director's chair vacated by HP1 and HP2 helmer Chris Columbus, it was always going to be a darker affair.

It is with its Hogwarts scenes shifting from their earlier soundstage artificiality to something genuinely atmospheric.

Cuaron also does a fine line in amusingly grotesque supporting characters and while not many, if any, have speaking parts, he seems to have a thing for decorating the place with dwarfs.

Nice place he's got there too - Hogwarts is now set against the Scottish highlands. While the school itself is newly dank and gothic, Cuaron and New Zealand cinematographer Michael Seresin also find the creepiness in the dappled sunlight of surrounding forests and lochs.

Likewise, the special effects are more captivating because they don't draw attention to themselves - the talking paintings look more like paintings now. In a dim light you might mistake the film's Dementors for a Ringwraiths from The Lord of the Rings but they are pleasingly nightmarish.

Likewise Hagrid's latest beastie Buckbeak the hippogriff (part horse, part eagle) is many more times convincing than anything the previous instalments conjured up. And Cuaron has a way of making Harry's requisite airborne scenes look and feel like something dangerous and gravity-defying, rather than an advert for the video game tie-in.

For those three or four of you who haven't read the book - and fortunately, it's not required for full enjoyment of the film - this one concerns Harry finding out a little more about the circumstances of the murder of his parents.

That involves one Sirius Black (Oldman), who has broken out of Azkaban Prison, the Colditz of the wizard world and may be making his way to Hogwarts.

There, life goes on as normal, even with those unforgiving soul-sucking Dementors - the Azkaban guards - standing sentry outside. Meanwhile the new Defence Against the Dark Arts teacher, Professor Lupin (Thewlis, who's great) takes a special interest in Harry's welfare and Hagrid is having some trouble with that new pet of his.

It does hit some puzzling flat patches along the mid-section as the threat of Sirius Black seems to abate. But into the final reels, its momentum builds neatly to its clever twist upon twist of conclusion.

Potter's young fans are growing up fast but this shows his flicks are keeping up. And Azkaban is the first of the films to really show that movies can be magic too.

Cast: Daniel Radcliffe, Rupert Grint, Emma Watson, Michael Gambon, David Thewlis, Gary Oldman, Alan Rickman, Robbie Coltrane

Director: Alfonso Cuaron

Running time: 142 mins

Rating: PG (contains scary scenes and mild bad language)

Screening: Village, Hoyts, Berkeley, Bridgeway