Adapting the 'Harry Potter and the Order of the Phoenix' novel for film was always going to be a nightmare. At 766 pages, it is the biggest in JK Rowling's series of big books about the boy wizard. Fortunately director David Yates and screenwriter Michael Goldenberg, both new to the Harry Potter series, managed to streamline the action down to a compact - and eminently watchable - two-and-a-quarter hours.

As fans of the films and novels will know already, Harry (Radcliffe, never better) is on an increasingly dark journey. From the opening scenes, '...Phoenix' plunges directly into an ominous atmosphere. Staying with his horrible aunt, uncle and cousin for the summer holidays in Little Whinging, Harry feels very alone. This is exacerbated when he is expelled from Hogwarts for illegally using magic outside of school. Although eventually cleared of all charges, when Harry returns to Hogwarts he realises that much of the wizarding community - encouraged by propaganda in the Daily Prophet - do not believe that he has witnessed the return of Voldemort (Finnes).

Angry with his friends, isolated from his mentor Professor Dumbledore (Gambon), plagued by nightmares and with a crush on classmate Cho (Leung), Harry is a bundle of adolescent anxieties as the stage is set for a tumultuous fifth year. Favourite characters return and gain new depth - although the condensing of the book doesn't allow too much time for development or exposition - and intriguing new characters are introduced. The sweetly sadistic Dolores Umbridge, played with great relish by Imelda Staunton, is appointed as the new Defence Against the Dark Arts teacher. An officious bureaucrat, she and her Educational Decrees swiftly take over the school, as she scoots around like a demented pink teapot, clipboard in hand. This film also sees the appearance of Termonfeckin's own Evanna Lynch, playing the fey and dreamy Luna Lovegood, and Helena Bonham Carter as Bellatrix Lestrange, one of Voldemort's more attractive followers.

The visual style is suitably grey and dreary as the children's world becomes more fearsome. But they intend to fight back. There are plenty of lively scenes as they train, under Harry's command, to fend off a potential attack by Voldemort. One of the more light-hearted moments is the Weasley twins' disruption of the Ordinary Wizarding Level (or OWL) exams, when they set off spectacular fireworks to disrupt Umbridge's rule.

If you're new to the whole Harry Potter genre, '...Phoenix' is not the place to start. Characters and events from the earlier films are referenced without any introduction, presupposing that the audience knows what has happened in earlier instalments. That said there is a most satisfactory darkness about this movie as the series moves away from the fun, carefree magic of the earlier films and into grown-up territory. Harry is no longer fighting outside enemies, he wrestling with fear of failure and the difficulties of growing up. Dealing, as it does, with more adult themes, this is not a film for small kids. But their elders won't be disappointed as they await the last two films in the series.

Caroline Hennessy