Cast: Daniel Radcliffe, Rupert Grint, Emma Watson, Michael Gambon, Jim Broadbent, Alan Rickman.

COMPARED to the thrilling shoot-out conclusion and fascist overtones of previous Harry Potter film Order Of The Phoenix, The Half-Blood Prince might seem like a bit of a let-down.

But the latest trip to Hogwarts School of Witchcraft and Wizardry is a well-paced and necessary calm before the storm that will be the series' two-part finale due out in 2010 and 2011.

While it won't win any new fans - watching the previous films is a bit of a prerequisite - the adoring herd of Muggles will be pleased with how the sixth book has turned out on the big screen.

Following on from the spectacular finale of Order Of The Phoenix, in which the Ministry Of Magic accepted that the evil Voldemort was back, Harry (Radcliffe) lays low over summer and wonders whether he should return to Hogwarts.

Coaxed back by Dumbledore (Gambon), Harry encounters the mystery of his potions book, the secret plottings of his classroom nemesis Draco Malfoy, and the trappings of school yard romances. He also meets the new potions professor Horace Slughorn (Broadbent), who may just be the key to defeating Voldemort.

Without many massive set pieces, except for the Death-Eaters destroying a London bridge and a fiery battle between Dumbledore and an underground lake full of Gollums, the sixth film bubbles along gently, building tension through its brooding cinematography.

As with the books, the films have become darker and more mature as they've progressed, and Half-Blood Prince takes it even further. The final act is devastating, as you would expect when one of the main characters is killed off.

Despite the increasingly grown-up tone, there are some excellent comedic touches to offset the bleakness, with the young cast again stepping up a notch in their performances. The only downside is that the film feels like a dynamic step down in intensity in order to prepare for the killer two-film climax, but that's to be expected and in the future this chapter will be highly regarded as the calming breath before plunging into the storm. Bring on The Deathly Hallows.