Potter enthusiasts are a loyal lot, but as the sixth title in the seemingly unstoppable franchise strides into our cinemas, even the most diehard fan will be asking the same questions. Does the latest Potter have what it takes to be the family film of the summer? Will Harry turn the Transformers into scrap metal and Ice Age into a puddle?

The answer would seem to be yes. The latest instalment is more of the same tried and tested formula to be sure, but it’s a formula that produces pure gold as far as the fans are concerned. The Potter movie experience is bigger than the sum of the individual talents that contribute to its making. David Yates, the director, orchestrates the picture with dizzying energy and confidence, but the might of the Potter phenomenon dwarfs his individual artistic contribution.

At the heart of the latest story lurks darkness — that and enough teenage angst and sexual frustration to fill a Quidditch pitch several times over. In this instalment both Harry Potter and his nemesis Lord Voldemort grow in strength. The pompous new staff member Professor Horace Slughorn (Jim Broadbent) holds a crucial key to understanding — and perhaps defeating — the fearsome power of Voldemort: Harry must seek the magical “horcruxes” in which the evil one has concealed part of his soul.

Meanwhile, although Draco Malfoy has been chosen for a deadly mission by Voldemort, the real danger comes from Severus Snape (Alan Rickman), who shows his true colours — all of them shades of black. There’s a lot of plot to cram into this instalment — J. K. Rowling’s novel was more than 600 pages in length — and, despite the weighty running time, the film occasionally feels a little hurried and perfunctory.

That said, the Hogwarts kids have matured. They’re as chaste a bunch or 16 and 17-year-olds as you are likely to find outside an Enid Blyton novel, but Harry and his classmates have awakened to the opposite sex. Ron Weasley attempts to evade the simpering clutches of Lavender Brown, a girl who appears to have learnt everything she knows about romance from the inside of greeting cards. And Harry might be able to kick a Death Eater’s bony backside, but he’s endearingly hapless when it comes to matters of the heart. The Chosen One is a bit of geek, although Daniel Radcliffe is growing into his looks, cultivating the pale, chiselled intensity beloved by Twilight fans.

This collective romantic awakening helps to flesh out the characters, making them infinitely more interesting for the adult audience. Kids, however, might not be so keen — a couple of 12-year-olds at the screening I attended squirmed with agonised embarrassment at the slightest hint of a snog.

Like many teenagers, muggle and magic alike, the Hogwarts kids have started experimenting with psychoactive substances. Ron is the inadvertent recipient of a love potion that has him hugging bits of furniture and grinning like a loon. And Harry swallows a vial of Liquid Luck and bounces off into a field looking as if he is trying to find the rave tent. But the teenage misbehaviour is just the light relief. Evil is permeating every corner of Harry’s world. The Half-Blood Prince is a name scribbled in an old textbook — a stranger whose scrawled notes fascinate and impress Harry, until he realises that they were written by one of his enemies. Given that this plot strand provides the film’s title, it’s dismissed in a rather cursory manner.

It will be no surprise to fans of the books that a key character dies before the end of the film, but I won’t give away the identity just in case. Suffice to say that the climax — a quest undertaken by Harry and Professor Dumbledore — is genuinely scary; and the shattered heart of the school hall, demolished by a vengeful Bellatrix Lestrange (an excellent Helena Bonham Carter), is a shocking, chilling image.

The film opens on July 15

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010